How to look up the previous years 1098-T box 2 amount from my taxes last year?

[KrisD]

You should have kept a copy of the 2017 1098-T with your 2017 tax file. You can print your 2017 tax documents including all worksheets and a 1098-T worksheet showing the entries (including Box 2) will be listed, but you may need to pay a fee to print last year's return. 

The easiest thing may be to get a copy from your school account.