InDesign can open and convert PageMaker files up to CC Version 8.
If someone is a CC (Creative Cloud) subscriber he has access always to the latest build of each version which is now CC 9.2 but can also install from CS6 8.x the latest build. So if you (or your company) is subscribing to CC they have to install CS6 manually so that your files could be opened.
The conversion can be very different, so I would strongly recommend to keep one old computer with PM on board, and that you create of each PM file a PDF to compare how it looked like before to adjust the documents after conversion or at least to be aware where things have changed.
We have Adobe Indesign CS6 (not the cloud version). I used it today to open a pagemaker file and it worked perfectly, however I was unsure that it would work after we uninstall pagemaker 7 from the computer. Oh and sorry for the late response.
Sent from my iPad
For InDesign you don't need PageMaker to convert files. But for your own security you might keep a copy on an old computer. Not every conversion is perfect, some are less.