how can i find out my passcode?

There is no place to find the passcode unless you wrote it down somewhere. If you've forgotten it, see the following.

There is an Apple article that explains what to do if you have forgotten an iPhone or iPad passcode. Click on the following link: How to remove your iPhone, iPad, or iPod touch passcode without a computer - Apple Support

If that option is not available, you will need to use a computer. See: If you forgot your iPhone passcode - Apple Support