Yes you can Lillian, but you will have to make a new folder with a unique name eg. Lilliem1, then you have to copy the models and jpg files from the folders they're in and put them in your folder. If there are 2 models with the same name eg model1.3ds, then rename one of them to model2.3ds (you don't have to write 3ds btw, that's done automatically). Make sure you copy the correct jpg files, if there are any for that model, into the folder or you'll get white bits. If there are 2 jpgs with the same name and they are the same picture you only need one of them, but if they are different pictures it will cause problems. A way round this is to name the jpg files to match the models, assuming there is only one jpg for each model, so model1.3ds has the texture file model1.jpg. If there is more than one jpg for each model this won't work.
Then use that folder in the editor and upload it with the level.
Sounds very complicated doesn't it, but you just have to follow basic rules that the models must have different names and you have to include the accompaning jpg files. The jpg files must have the original name or a name that matches the model name. The texture filename is assigned during the modelling process and can only be changed in a 3d application unless you change it to model#.jpg.
Usually, models I've made have a readme file telling you which jps go with which models so you shouldn't have a problem there. If you're unsure which goes with which, try a test with each model on it's own with different jpgs and see which ones show up in the game. If the model looks white anywhere, it is the wrong jpg, assuming it's not meant to be white obviously.
I bet you wish you'd never asked now, don't you?
If you're having specific problems, let me know and I'll try to help you.