If that is a Grayling, MI, manufactured Grizzley, you can take the side plate material off and the actual draw weight will be written there. Generally, a 50# Griz will be within about +/- 2# of the visible markings. Bear usually marked them at 5# increments at 28" of draw. Even custom bowyers are often off by a pound or two, so that's no knock on Bear bows. I don't know if they still mark under the side plate on the Gainesville bows or not.
BTW, I agree with those who are recommending starting with something around 40# at your draw weight. Some guys draw is shorter with a traditional bow than with a compound. Mine is exactly the same with either a compound or a recurve, so don't assume anything.
The best way to know for sure what your draw length is would be to put a tape mark at 28" on an arrow that you know will be long enough for your draw, then either have someone watch you shoot, or better yet, have them record you while you shoot. Then compare your draw to the tape mark. I CAN draw to 28" or more quite easily, but when I'm actually shooting at a target using proper form, I find that I am actually drawing 27".
Oddly enough, that is exactly what my draw was when I had the dealer set up my compound bow for me. Yeah, I've been to the dark side when elbow problems made drawing with my fingers too painful to tolerate. Thankfully, I've managed to heal up well enough to shoot traditional, although I have had to drop down to 45# @ 28" to do so. I found the joy of shooting just wasn't there with the compound. Although it was much faster and I could shoot it very well, it just felt wrong to me. The element of skill was all but gone, as was the sense of accomplishment.
Anyhow, the Grizzly is a fine bow. Keep the 50# bow and find a lighter one to start with as the others have said.