Preset Folder

You'll have to give more information, otherwise we may give you the wrong answer. So first of all: what version of Lightroom are you using now and what version were you using before? Next, what kind of presets are these (what is the file extension)? And finally: in what location did you place them?

And, depending on where the preset came from (internal to LR, or a third party), you may need to import them, even if they are in the correct folder.

And have you clicked on the + top right of the presets panel, then clicked manage, then seen if they apper but need to be marked as to show up in presets?