Hello Christine

while self-efficacy is my area of expertise, applying in to couselors is not. However, after a quick search on Google Scholar I found the following article:

Article Self-Efficacy of Beginning Counselors to Counsel Clients in Crisis

It is listed with more then 60 citations on Google Scholar so, hopefully, I will prove to be a good starting point for you. I reckon that you will have to tailor any instrument you come across to your specific research questions.

Best of luck

Marcel