Source: How to check the current OpenCore version?
Open up the terminal, and slap this bad boy in there:
As of OpenCore version 0.6.4, you should see some output, followed by
Release 064 and the date of release are listed. (If you feel like your upgrade went well, but this isn’t reflecting the correct version, you might need to flush that vram. Upon that not working, following the Dortania Guide for your specific build is advisable).