How can I find out if I have a 401k and how much do I have

A 401(k) is a benefit provided by SOME employers. So you need to contact your former employers that offered the benefit. You should have been getting regular statements if there was a balance. You can also contact the SSA. Companies are required to report to them if you have any retirement benefits.

Are you working now? Are you retired? Most workers know if their employer is taking out money for a 401K account, and even know if the company is matching it. If you don't know already, I really doubt if you have one. That is just my opinion, and I am sure there are many. Good luck. Call your past employers, and present employer, if working, and ask.