Hello:
The POF files were the little image preview files; not the linetypes themselves. [/shakes cobwebs out of brain]
The linetypes were always all lumped into one file, called Dcad.LIN (in the DOS days...). If you can find this one, and can import it, then you'll get a separate LinetypeName.DLT file for each included definition.
If you don't have these, it is
very easy to recreate linetypes in v11 -- and you can probably make improvements on them. Try out the Linetype Creator: work from left to right, and draw the spacing at the scale that you want it to appear -- and set the spacing to be the same length as the repeat in the definition.
Just draw one repeat segment from left to right, click the begining point, select the entities, set the spacing to the same as the repeat segment length, pick the end point, name it -- and you're done.