Transferring iTunes playlists from an iMac to PLEX running on a Synology NAS



I have had a Synology NAS 218+ 2 bay drive for several months now and I am yet to conquer this persistent issue. Running two 8Tb drives (mirrored), the intention is to transfer my entire music library (6Tb) from my iMac to my NAS - but most importantly, with the ability to transfer my extensive set of playlists in .m3u format which I can then access from my NAS. I have a Cambridge Audio Network player (AZUR 851N) to play music from the NAS. I have a full Plex Pass

Can anyone tell me how to achieve this? I am sick of trying. I was under the impression that all my iTunes playlists would be copied automatically to my NAS, especially as I am a Plex Pass holder. Disappointed to find out that that isn't the case. Digital music libraries are effectively useless without playlists...I have something like 25 playlists, all curated by myself over YEARS, (the largest of which is 1400 tracks, the smallest 50 tracks) and need to access said playlists from my NAS - otherwise, it's useless to me.

I have tried to contact PLEX, however seemingly they have deliberately made it impossible, not listing a customer support telephone number (really????)

I have spent a while scouring the forums for guidance but there's nothing that helps