You can easily find out if you have a look at the damper itself. There is a serial number on it. Copy the serial number and paste it into the rockshox trailhead app (or webpage).
So first of all: 3500 pounds for an e-bike isn’t that much. It’s basically entry level. The first search for your headset would have given you just the information you need.
It’s ZS44/28,6 and ZS56/40