Hello, a client of mine was going to leave a review but told me he needs my TER ID to do so. How do I find this? Thanks in advance for the help!

If you don't have reviews here yet you don't have an ID number or a profile, he will establish your profile when he answers the qusetions on the review and then TER will assign you an ID number. Even if you do have reviews he doesn't need your ID, the ID field is an optional field and can be left blank.
 Just as a heads up, if you don't have reviews and he hasn't written any yet TER may not accept his review right away and may hold it until you get one from an established reviewer.  

THANKS! I will try this