I need to hang a mirror in my bedroom. I purchased some anchors assuming the drywall would be 3/8ths of an inch thick. However, when I drill my pilot holes, I realize the drywall in my bedroom is definitely more than an inch thick! I live in a residential condominium tower (35 stories high) and the wall I am drilling into is one that I share with my neighbour. At this point I don't know how thick the drywall is, but I know I'm not drilling into a stud.
So assuming this drywall thickness is normal, should I continue to use the anchors that I bought? See picture below. These anchors require a hole that is 1/4 inch wide but since I'm not confident in using these anymore I've stopped drilling. What should I do?