Hi there! newbie here! (I have a robo3d printer, if that helps)

Ive extracted some pieces off a model from League of Legends to print for cosplay and im having a bit of trouble with the sizing and also getting it to look right in the printing software. I was able to get a couple items to print correctly, but I am not a wiz when it comes to 3d software.

I printed a bracer and with some help from the internet it came out decent but the top and bottom of the bracer filled in and i wasnt able to figure out how to stop that from happening.
Bracer
Bracer Model

I also have some armor that i would like to print but I am not sure the best way to go about it.
Armor Model

The sizing is also confusing for me as its not calculating in inches or cm (im assuming its mm?), and theres no designation on the MatterControl software or in 3Dstudio Max as to what the sizing convention is for the model. I looked on the webs to try to modify the sizing in 3DS to inches or something I could easily recognize for sizing the model but was unsuccessful in doing what i needed.

Any help would be greatly appreciated!
Thanks!