This converts 3/4" NPT to 3/4" GHT to accept standard garden hose threaded connections. This is what you need to go with the T-304 Stainless Elbow and T316 Stainless Bucket Filler Hose or Inlet Hose. 

Here would be your Flow Path if you're doing a stainless inlet hose setup: 

Hose Bib > 3/4" Female GHT Coupler > 3/4" Male GHT Plug > 3/4" Female GHT to 3/4" Female NPT > T316 Stainless Bucket Filler Hose > T-304 Stainless Elbow > Brass 3/4" Male NPT to 3/4" Male GHT (THIS PART) > 3/4" Female GHT Coupler > 3/4" Male GHT Plug > Pressure Washer Inlet