I see no one has responded so I'll jump in without this trailer and estimate like many others, 23-24"'s.
Get an adjustable hitch so you can move it up or down to get it level.
Some factors to consider will be the type of truck and sag, weight dist hitch, weight distribution inside trailer, trailer tire size, etc.
Most of the time it's really a trial and error approach but take the time to get it right. Be sure to get the 10-15% tongue weight. Find a scale if necessary.
Bob and Better Half
2007 F-250 PSD, SW, CC, LB, 2WD
2006 TF32SS Cross Terrain Toy Hauler (sold)
Reese 16k slider