E-3-Fifty? A Class C with a Van Cab, right? It has an AntiLock Brake System (ABS) with an ABS Sensor Cable that looks like this
in addition to a rubber-covered brake hose. The ABS will not engage the brakes. It only monitors wheel speeds and decides to release a wheel that's going slower than the rest, on the premise that it's sliding.
Front brakes are dual-piston disk.
Rears are conventional drum with foot-operated parking brake.
Can you safely jack one corner up, at a time, blocking the opposite corner? You should be able to turn each front wheel. If not, you can bang on the caliper with a mallet or hammer against a wooden block. Then try again.
For the rears, one side should turn IF you have transmission in Neutral and Parking Brake Off.
If you don't feel you can do these checks safely, please call for help.
When you have more info, let us know.
