I have a Peavey T-Max 210 combo.
I also owned a BAM combo. There is no 1/4" speaker jack on the cab itself, so you have to get a 1/4" coupler (female to female). Then unplug the speaker cable from the combo head and plug it into the coupler. Then plug a speaker cable from the BAM head to the other end of the coupler.
Or, you can do what I did. Unscrew the 210TX combo's electronics plate (where all the connections for the crossover and wiring for the speakers and piezo are). Then cut the 1/4" male plug wires off and pull the wire out of the cab. Then get a female 1/4" jack and wire it up to the old 1/4" speaker connection (on the back side of the plate you took off) and mount the jack to the cab.
Now you can use it as a combo, or as just a cabinet easily. I cut the amphead section off my combo (and re-covered) and just use my T-Max head seperately now. The 210 is much lighter now without the head and the cabinet part that held the head. Plus I can use my T-Max head with anything else without dragging that ungodly heavy combo around.
You'll love the BAM. I owned the BAM 210 combo and in over all the 25+ years I've been playing, it's the only amp I've ever regretted getting rid of.