Create Group if Field Contains

I am very new to SSRS.  I'm trying to create a report to count daily jail population by current housing unit.  Right now the housing description field is separated down to the bunk.  I need to group these by larger housing unit and count the total inmates assigned.

Example:

AGENCY JAIL CB.9 CELL 910 BUNK1

AGENCY JAIL CB.9 CELL 910 BUNK2

AGENCY JAIL CB.9 CELL 910 BUNK 3

AGENCY JAIL POD.F DORM 1 BUNK 103

AGENCY JAIL MDW.EAST CELL 100 BUNK 1

I need to group these by the CB.9, POD.F, MDW.EAST part of the field and count the total inmates housed.

How do I do this in SSRS?

Thanks!