Given the amount of description you gave about your configuration I'll give you a similarly descriptive answer: mount it.

What format is the HDD ?

Have you mounted it ? If not, Google how to mount a HDD in Linux.

If its mounted and you can't see it in Plex itself, then we'd need more info such as steps you've taken, configuration etc.

We're geeks, not mind readers :)

As above and also; how are you running Plex?

For example; I run it via docker and there are extra steps to have it show up in docker. But there's no point in me describing this if you're not as it'll just complicate things.

Have you added the path to your media, on the new drive, within Plex by adding a library for it?

If not:

 

1. Log into Plex
2. Go to settings
3. Under Manage select Libraries
4. Click Add Library
5. Choose the appropriate type (e.g. Movies)
6. Give it a name (e.g. More Movies)
7. Click Browse For Media Folder
8. Find the one you want, select it and click Add

nzkc:

 

Have you added the path to your media, on the new drive, within Plex by adding a library for it?

 

If not:

 

 

1. Log into Plex
2. Go to settings
3. Under Manage select Libraries
4. Click Add Library
5. Choose the appropriate type (e.g. Movies)
6. Give it a name (e.g. More Movies)
7. Click Browse For Media Folder
8. Find the one you want, select it and click Add

 

Yip, this - you need to tell plex where to search.

Plex will also need permissions to your folder(s).

Typically plex runs as the plex user within the plex group. Therefore; I make it the owner of the library folders. You can do that with:

chown plex:plex -R /mount/media/plex/

(or whatever your path is).

I also add myself as a member of the Plex group:

usermod -a -G plex yourusername

And if needed, grant the group write to your media folder(s):

chmod g+rw -R /mount/media/plex/

Hi again having problems  with first command     maybe if i say where my media is  its on a hd called 640   which is  in /media/d

so what will first command be?   chown plex:plex -R /mount/media/d/640  which  it doesnt find.

one of my other drives which shows in plex  is /mnt  volume linux

I'm a bit confused from your screenshot.

Can you provide the output of the following commands (because I suspect its not mounted):

sudo lsblk

sudo blkid

sudo cat /etc/fstab

Legitimate bookmarks for a legitimate businessman.

i ran that in terminal and got cannot find,

how do i mount to different place?     thank you

if it helps