How to unlock disabled iPhone ona different iPhone

You will need to use a computer. See the instructions in If you forgot your iPhone passcode - Apple Support including the following:

This process requires a Mac or PC. If you're using a PC, make sure that it has Windows 8 or later, and that iTunes is installed. You also need the cable that came with your iPhone, or another compatible cable, to connect your iPhone to the computer.

If you don't have a computer and you can't borrow one, you need to go to an Apple Retail Store or Apple Authorized Service Provider for help.