Step 1:
Install SimC addon – https://mods.curse.com/addons/wow/simulationcraft
Step 2: Copy your character information from typing /simc
Step 3:Paste the information into a new Simulate tab
Step 4:Set up a copy and replace the gem_id with the relic id you want
MAKE SURE YOU DELETE relic_id=
If you’re going to be gaining or losing item level, add ,ilevel=What the weapon ilevel would be
Step 5: Press Simulate and wait
Just Nots Thoughts 