How do I extract speedtrees as obj files? I need to get them into blender. Usually tsrw lets me export stuff as obj files, but all the plants seem to be some weird thing called "speedtrees" that won't load properly in tsrw and can only be exported as bin or spt format. Most of the textures are labeled as "missing" when I try to load them and the program won't display them in the model view. I'm finding lots of tutorials for retexturing these "speedtrees" but none of them cover exporting the mesh.

The only thread I can think of that might be helpful is this one:
https://modthesims.info/t/showthread.php?t=455516

That topic seems to be about doing things in speedtree, whatever that is. I need them as obj for blender, not spt for this speedtree thing. tsrw will already spit out spt's, but that's not a format i can work with. And none of the converters i've found will convert a spt file to anything. They all say it's an unsupported format.

The speedtree meshes are for all of the items in game that are affected by wind movement (flags, trees, bushes etc), that's the format they are in for Sims 3. You need Speedtree (as described in the thread I linked) to be able to edit those. If you want to be able to convert those to a different format, maybe search for Speedtree tutorials instead?
https://docs.unity3d.com/speedtree-...ual/meshes.html
Of course you'd need a copy of Speedtree, I don't know if that's available free any more.
You could potentially use 3D tree models from other games (Sims 2 for example) in Sims 3, but they wouldn't sway in the wind and would behave just as a decor object.

The topic also says you need old speedtree, not new speedtree, and unity's only offering the new one. The trees don't need to be animated. I'm trying to convert them from ts3, 'cuz i'm rebuilding a lot i really like that i had in it. I've converted or found conversions for everything else, but i need these trees. There aren't any that look close enough.

You can use wayback machine to get the version of the unreal development kit that was available from the link by Keckhs in that thread, from that date.
https://web.archive.org/web/2012052...dk.com/download

Oldest one seems to be from 2009. I'm not sure how much you can do with the development kit version.

I found this, not sure how useful:
https://github.com/RetiredSDK/speedtree