Hi,

In the past i did install some sim3pack lots without cleaning them first. I did uninstall those lots, but now I have my catalog with these objects and can't seem to find where they are located. They don't show in my launcher nor exist in my mods folder. I was looking online to find a solution but so far, nothing. Can someone help on this please? thanks!

They're in the Library folder (Under Your Documents/Electronic Arts/The Sims 3/Library)

The challenge there is all the file names are randomly generated, so you won't be able to determine what file has what pretty easily. However, I think you can delete these lots directly from the bin file while in "Edit Town"

As simb0t explained they can be deleted from the bin and that will remove the file from the Library folder however if you have any of those lots placed in a world they will remain in the world until you bulldoze them.
A good practice for managing those library files going forward is as soon as you download and install a lot or just copy an existing Lot to the bin, go into the Library folder and rename the lot to something you will recognize; i.e. LargeFarmFromMTS.package or if it's a household: MitchellFamily.package. This can be done while you are in game. If you have other unnamed lots already in the Library folder sort by date and the one you just installed will be at the top.