You can't possibly "know" God exists. You can't provide any evidence, failing to meet the criteria of "knowing." You believe God exists, have faith that God exists. Slight difference.
Can I prove God exists to someone who doesn't want to believe in Him? No! His word says He has to be accepted by faith. Everything God does for us and expects from us is by faith. Do I know He exists? Well either He does or I've lived a charmed life or have magical powers?
When I was young my family lived in an apartment on top of a building called the "Floor Store", one winter day I started down the stairs which were iced over and lost my balance, I was going to fall and there was no way to stop it, all of a sudden for no reason I could figure out I just straightened back up, I was just as amazed by that as I was frightened that I could have fallen to my death.
On my way to school once, I had a pack of dogs surround me growling at me, for no reason I could figure I just barked and the dogs scattered, I don't know why I barked, I don't know why they scattered??? (Other people might think I look like a dog but my husband doesn't and that's all that counts).
I came from a poor family and college didn't seem to be an option for me, but I graduated from an Assembly of God college and didn't have to pay much back on my loans because I taught for a while in low income schools.
I had never been to a dentist till I was in my 20s, before I went I prayed that I wouldn't have a lot of expensive dental work, after having my teeth cleaned the dentist was amazed not to find any cavities, I've since had only one and I think I should have gotten a second opinion about that.
When my husband and I decided to move from an apartment to a house we didn't have a lot of money, we kept going by a house that already had appliances, my husband was reluctant, but we decided to go for it anyway, we didn't have the down payment and we were not allowed to borrow the money because that would be another debt, there was no one to borrow it from anyway, before closing my husband got a letter about an insurance policy his mother took out on him as a child, he cashed it in, that covered the down payment, we bought the house in the 20s it's market value is now in the 90s and it's paid off. By the way we prayed for all these things.
My nephew got in trouble two or three times for drugs, before the last time he was told if it happened again he would go to prison, his mother and I prayed, his former lawyer who used to be a judge was pretty much through with him by the time he got in trouble again, all of a sudden he changed his mind and decided to help him, he spent a few months in county jail but didn't have to go to prison, no one, even the judge understood why everyone was being so lenient with him, anyway he decided he didn't like jail or prison and hasn't gotten in any more trouble and that's been two or three years ago.
God gave me a little bit of a computer program at work, that I worked at and revised with His help till I got all the forms I work with on one program and can fill them out from one data sheet, and I had no formal training that way at all. Other people also use them and depend on them now, they don't want to go back to typing the forms on the typewriter.
These are just a very few of the prayers God has answered for me and things He has helped me with. I may not be able to convince anyone there is a God, but no one will ever convince me there isn't one. There's just too much evidence in my life experiences that He exists and that He cares about me.