Getting BACK into FOUNDATION! Matching?

du

I’m trying to get back into foundation. I have a love/hate relationship with it.

I have combo ACNE prone skin. I’m going to get the L’Oreal true match, and I’m going to Walmart to get it.

Only thing is idk what my skin color/tone is?

Am I allowed to open it in Walmart to match it to my skin??

How else am I suppose to know if it matches or not?