I only have access to the music i purchased in iTunes

If you see only the songs you purchased, you are probably accessing those songs from Apple's iTunes Store servers (also called "iCloud"). Purchased songs are made available to you, to download or stream, on any computer (running iTunes) or iOS device (like your iPhone and iPad) that you associate with your Apple ID. So, if you get a new computer, you can run iTunes on it and access your purchased songs immediately by associating that computer with your Apple ID. You don't need to download songs to the computer.

Based on the info you provided, my guess is that your Mac is that "new computer." I don't know if the work you did ("I spent months burning several hundred of my cd's to a hard drive") was before or after getting the Mac. But currently, it sounds like your iTunes library is only able to access your purchased songs. They are being accessed from iCloud, not from your Mac's local drive.

You can check by doing a right-click and Get Info on one of those songs in iTunes. On the Info window, go to the File tab. Find location. Does it give a file path to where the song is stored on the Mac's drive, or does it say iCloud?

Some other points that need clarification...

- On the Mac (since getting it), did your iTunes library have those songs your imported from music CDs? Or was that on your previous PC, and not on the Mac?

- Do you subscribe to (pay for) either iTunes Match or Apple Music? These are two Apple services that provide an iCloud Music Library. Otherwise, you do not have an iCloud Music Library, and only your purchased songs are accessible from iCloud. Your other songs (like the ones imported from CD) are only stored locally, on the drive of the computer used to run iTunes.

- Do you still have access to the previously used PC, with its iTunes library intact?

The lesson to be learned here is to make backups of anything that is important to you. It appears that you did not have a backup of your previous computer. If you did, you could simply restore the backup (or migrate it, if it were from a Windows computer) to your new Mac.

For the remaining songs, I guess you'll need to re-import them from CD. You'll need an external USB optical drive, if your recent Mac does not have a built-in optical drive.

Macs have a built-in feature called Time Machine, which automatically backs up your user data (including your iTunes data) to an external hard drive. It does this as a background process, so once you set it up, you don't really notice when it happens. You should buy a large-capacity USB external hard drive and turn ON Time Machine going forward. Then, if you delete a song (or word processing doc) by mistake, you can "go back in time" to get it back. Or if your Mac (or its drive) fails, you can restore "everything" from the Time Machine backup.

Additional note: If your old PC won't turn ON (that's the reason you got a new computer), you may be able to remove its hard drive, put it in an inexpensive (empty) USB external drive enclosure, connect it to your Mac, and access your old data (and not just your iTunes data). If that works, you can add your existing song files to your Mac's iTunes music library (instead of having to "rip" them all again on your Mac).

AND, if that hard drive is large enough in capacity, after copying off all the data you need to the Mac's drive, you can Erase that hard drive (using Disk Utility) to reformat it for Mac. Then, use it as your Time Machine backup drive going forward.

Did you copy everything from your old computer, or your backup copy of your old computer to your new one?

They will not magically appear. You have to put them there.