ok so i was originally in riverview. then i used traeler to move to bridgeport. then after a while i moved back to riverview.
so i have 3 saves now. one riverview before moving, one brideport and my recent normal one in riverview.
can i delte the old riverview save folder and its backup folder?

Yes, you can delete the saves, in the sense that doing so won't have any effect on your current save. But it's a really good idea to keep backup saves in general—you never know when a game-breaking issue might show up, and it's often easier to revert to a previous save than to try to fix the problem.

When saving, you can choose the "save as" option and rename the save, and the original will remain as a backup in case you need it. I generally use "save as" at least once a sim-day, and I periodically delete all but the last 4-6 saves. I've had to use backups a number of times over the years, and it's great to lose only a sim-day or two rather than having to start from scratch.

The above is also the strategy suggested by the Saver mod. The game never reaches into saves other than one currently loaded up for data, those are only there for us to use should they be needed.

but i thought i would need to keep the bridgeport save in case i wanted to travel back to the same town ?
and so deletig the first riverview will not affec my current game?

Look in your Saves folder in your TS3 user game folder in Documents, inside the actual saves. Each save is actually a sub-folder. You will see that one save, let's say the one you are playing forward no matter what you have called it, contains nhd files for your current and each of your connected worlds and a TravelDB file. The foreign sim data is all there, self-contained within that one save. The game does not reach across game saves when a travel transition happens, what it does is gracefully (in theory) remove the currently being played nhd file from in-use memory (RAM) and load up the nhd file of the destination world, then begin simulating that one instead.

Deleting older saves will never affect your current ongoing game. We only hold onto older saves, maybe, if we might someday want to load things up as they existed earlier in the timeline.

Thank you for your help