... So I need a function in columns B,C, and D to split the numbers in column A that are seperated by a comma followed by a space...
Typically you would use Text to Columns from the Data tab's Data Tools group but this will put the results into columns A, B and C. If you need the original column intact, copy it to column B, select column abd use
Text to Columns, Delimited, Comma, Finish. This operation could be recorded as a macro for future use.
Combinations of LEFT(), MID() and FIND() could also be used, but the complication is the varying number of digit sets that are comma deliminated.
Edit: the following formula will work for ~15 numbers sets in the format that you have shown in your sample, e.g. <six digits>, <six digits>, <six digits>, <six digits>,etc. Just put it into B1 and
fill right.
=TRIM(MID(SUBSTITUTE($A1,",",REPT(" ",99)),1+(COLUMNS($A:A)-1)*99,99))