There are lots of ways to mount a ship model. Many people like brass pedestals, which are available from firms like Model Expo and Bluejacket. (Quite a few modelers get by with modified brass lamp finials from the hardware store. I have no idea whether such things are easy to find in Taiwan.) The Pamir was a long, relatively skinny ship. I’d suggest three pedestals.
Another nice - and slightly easier - way to do it is to make a series of “keel blocks,” suggestive of a ship that’s sitting in a dry dock. Get hold of some nice hardwood, perhaps about 1/4" square, and chop it into lengths slightly longer than the model’s beam. (In the U.S., the easiest wood to find in hobby shops is basswood. It can be made to look pretty nice with the help of stain and varnish. Pine is also ok; maple, walnut, and cherry are better. Just about any hardwood you like will work. But strike all memory of the term “balsa wood” from your mind.) Glue the blocks down to a nice baseboard. (If you’re the woodworking type, you won’t need instructions on how to make a baseboard. If you’re not, maybe a friend can saw one out of a board and rout the edges for you. As a last resort, the ship model suppliers sell them - but at a pretty high price.)
Whatever mounting method you pick, you’ll need a system of fastening the model to it that’s both sturdy and removable. (You don’t want to mount it for good on that nice baseboard till it’s finished. Till then, mount it to a piece of scrap plywood or something.) That means drilling some holes in the bottom and providing something for either screws or bolts to screw into. You can epoxy a piece of wood inside the hull bottom and fasten the hull to the baseboard with wood screws, driven in from the bottom. Or you can epoxy a couple of nuts inside the hull bottom and do the job with bolts. That’s a particularly good option if the bottom of the hull is relatively flat - which, as I recall, the *Pamir’*s is. If the hull bottom has a lot of deadrise (i.e., if it slopes upward sharply from the keel), it probably will be easier to shape a piece of wood to fit inside it.
The rigging lines I listed earlier would be a good start. (You’ll probably want to add a few more; I didn’t, for instance, mention any of the ones that control the spanker boom and gaff.) Start out by installing enough rigging so that none of the masts or yards looks like it’s unsupported or free-swinging. I suspect you’ll conclude, after you’ve gotten four masts and their associated yards, booms, etc. into that condition, that you’ve done enough rigging for your first effort.
The Underhill and Villiers books should make the basic nature of rigging clear. It’s far easier to explain with the help of illustrations - which both of those books have in abundance. Another book I strongly recommend is Seamanship in the Age of Sail, by John Harland. But if your budget is limited (as whose isn’t?) I think the first acquisitions I’d recommend are Underhill and Villiers.