I'm not sure what you mean by "prims".
Obj = 3D model
Bmp = bitmap (a 2D image file)
You can create a 2D image, (tga, bmp, jpg, png, whatever), by rendering a view of a model. There are several model types that A:M can import as props of which Wavefront "Obj" files are just one. You cannot just load obj fles into A:M however, you must right click in a model window and choose plugins\import\obj but you must have the obj plugin installed in you hxt folder first. I'm not sure if the obj import/export plugin comes as standard with A:M these days. I know that it was third party in the past.
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Here is a link to Arthur Walasek's A:M plugins, which include the obj importer that you will require:
Arthur Walasek's Plugin Page
"Prim" is short for primitive; a prim is a single unit of any shape/size, used for building in some virtual worlds. So, I am trying to take what I create in A:M out; I will take a look at your link. Thanks very much for your input.