First things first: a ";" is text, too, so what you might want to do is to either

1. split your string of the first column and then count it with TEXTSPLIT (which unluckily doesn't work in my excel version)

2. count the ";" indirectly by counting the length of the original string, deleting all ";" and then subtracting the new length

   =LEN(A1)-(LEN(SUBSTITUTE(A1,";",""))

source: Formula in Excel to count occurrences of substrings within strings