I'm trying to do a backdoor Roth IRA conversion but gpt is telling me I already messed up and I'm not sure how to best move forward. I contributed 7.5k to an existing tradition IRA I have, which had 40k already in it. Gpt is telling me I needed to contribute it to a new empty IRA account. What happens if I transfer the 7.5k to a Rorth IRA? Will I need to pay tax? On how much?

Gpt is wrong here. Doesn't matter if it's new or empty, the same complications kick in. You'll need to follow the pro rata rule if you have traditional PRETAX IRA money in your name at the time of the back door.

You will have to pay tax on the majority of the 7.5k converted under the IRS pro-rata rule (as ordinary income), as Baruch mentioned.

well, it might not be the majority, it depends how much is in there.

Baruch is 100% correct If a Roth conversion or traditional contribution doesn’t make sense, you can still unwind the contribution without incurring an excise tax through something called removal of excess.

So is it it best to convert the entire balance this year so we don't run into this issue going forward? In spouse account there is only $500 but in mine there is a little over 50k. An I allowed to convert the entire 50k to Roth IRA? What will the implications be?

depends what year you expect to have the lowest income. you want to convert in years you are in a low tax bracket. if doing the whole thing at once moves you up a tax bracket don't do the excess. if you are in a higher tax bracket now than you'll be in the future, wait.