I am trying to use some of the MMF 1.5 extensions but they have a different file type. I put them in the "MMF 1" folder in the MMF2 directory, but they still aren't working. What do I do to make them work as they would in MMF 1?
Short answer, you can't; they're a different format. The /mmf1 folder is there so that projects containing MMF1 extensions can be opened in MMF2, but you won't actually be able to run them.
Which extensions are you needing to copy over? A fair amount of MMF1 extensions have been ported directly to MMF2, and there are many more that improve on the originals.
I believe the Platform Swing object was designed for MMF2 from the beginning, so you should be able to find an MFX version of it. I'm not sure about Drawline, but you can get the same effect with the Overlay object anyway.
I don't see the platform swing object, unless it is by a different name. I know when I found it on http://www.clickteam.info/extensions/ it was only a .cox. There isn't a corresponding .mfx object on the website you provided.