@3_rolyat_3 There are a few things to cover here. The first is that the transitions in TS3 are delicate and can go wrong in a number of ways. By the time you arrive at the destination and your sims aren't there, the game is already borked and should be quit without saving. Hopefully, you have a backup save of two that you can use, or at the very least the automatic backup that you can find in your saves folder. Now would also be a good time to make copies of your existing save(s). Preventing this kind of error going forward is certainly doable, although it's hit or miss without mods.
It takes extra resources, expecially RAM, to load a second world in addition to the one that's been active. So the usual steps to reduce the load on the game are to only travel right after you load your save (when RAM use is lowest), and to put all of your graphics settings on low until your sims arrive. (Then you can change them back.) Other steps that can help are emptying out your sims' personal and family inventories as much as possible.
As far as mods go, I'm not sure where you were looking, but you shouldn't have to pay for anything. The mods that reliably fix the travel transition are NRaas Traveler, accompanied by ErrorTrap and Overwatch. (Nraas also hosts a mod called MasterController, which is very useful but does not directly influence travel.) They are free, and your computer should already have the software necessary to unzip them.