How do I create a formula to count multiple events in a set time period ex 8 am to 10 pm

Hi Wallardyce and welcome to the forum,

Look at Column D for a new "Helper" column and the formula I think you need. Your times need a space between the last number and AM or PM. That is the first problem. Then converting the to time and rounding down to two hour shifts.
See the big formula in D2. I've also done a Pivot Table and Chart so you can filter the group and see the times.

=HOUR(TIMEVALUE(TRIM(MID(SUBSTITUTE(SUBSTITUTE(C2,"AM"," AM"),"PM"," PM"),11,25)))) - MOD(HOUR(TIMEVALUE(TRIM(MID(SUBSTITUTE(SUBSTITUTE(C2,"AM"," AM"),"PM"," PM"),11,25)))),2)