Is there a hashtag on the English wireless keyboard? I have a wireless keyboard and can't find the hashtag. I have found it on my iPhone but can't find it on the mac keyboard
If  Shift 3 doesn't produce #, then try Option/alt 3.

Another less likely possibility is the \ key at the far right.

It all depends on which layout (US/ABC, British, British PC) you have active in system prefs/keyboard/input sources.  Change it to the one that matches the printing on your hardware.