As long as you use PVC pipe to connect the the two fittings. PVC-Lock fittings are designed only to connect with PVC pipe itself, not with fittings like this.
3/4 is the pipe's internal diameter. You don't usually have to measure it, pipes are clearly labeled. The "slip" portion of this fitting will accept a 3/4" PVC Sch. 40 pipe
Gualts, this fitting is designed to fit with a garden hose, so you would need to make sure that the steel hose has the exact same dimensions (size, thread, etc) first. Additionally, this fitting is only for outdoor use with cold water only.