Listen carefully,
First thing you do is double click on my computer to open it up >then open the hard drive that you have FL3 & 4 on up>
click View>explorer bar>folders ( your screen should split to two window, one for the currently open folder and a explorer for your whole system.
Next open the folder FL4>whatever until you get to >collected. Once you've done that, you should see all the folders in your updated FL4 collected folder. Now go back to the left and search for you FL3 folder ( do not open the folder by clicking on them otherwise they will open up in the right window, use the + & - sign to view folders in the explorer on the left side. You want to keep the FL4 collected window open at all time because when you find your sounds, you will select and drag them to there new location (FL4 collected). So only open the folder in Fl 3 that's collected, select everything in it, and drag it to the right side of the window. Watch out for kits with the same name, and kits that FL have upgraded from version to version. Start up the program and you should have access to your sounds.
This is really about how you can use explorer for easy access to all your files, without opening alot of windows. This will also help with organizing lots of other stuff. Hope I helped
Eka way might be more simpler, but I like my sounds in my software