Best thing to do is to find out what the Cisco is configured for, and match that. If nothing is configured, the default is "Digital Link" or mode 0 in IOS-speak. Per CCO, here are the 4 options:
0: Digital Link, the default setting
Keep in mind that the point of subrate compatibility settings is that different vendors implement subrate DS3 in different ways. However, since all vendors should implement full DS3 in the same fashion, I recommend asking the service provider to turn off the subrate temporarily if you have problems bringing up a circuit as a troubleshooting method. So even if you have mis-matched DSU modes, the circuit should come up as a full DS3/44210 kbps if there are no other problems.