Formatting SSD for new Macbook Air

[badshoehabit]

Hi, long time no see.

Replaced my very old, still functioning MBP (2016) with a Macbook Air a few months ago. Like it very much: still issues loading all my photos but current issue is that I can't get my Seagate Ultra Touch SSD formatted. Followed various notes but lost. Drive recognised but won't mount so can't do a back up. Tried Cmd+R on start-up, nothing appears other than log in. I've erased it but no prompt for what's next. Screenshots of what I experience. What do I do next please?

 

[MacInWin]

In Disk Utility, click on the "View" button on the menu bar, then select "Show All Devices." Once it shows all the devices, select the top level of the external drive, which should show as the actual manufacturer name and model. Then click on Partition and create one single APFS partition on the drive (Note: That action will erase the entire drive, so be sure that if there is something on it you want, you get that off first.) Give the partition whatever name you want. Choose GUID as the Partition scheme.

Once it has run, you should have a single Container on the drive and in the container is a single Volume, with the name you chose for the drive. That volume should now mount.

Now open Time Machine settings and point to the newly formatted drive as the target. TM will take over the drive and add additional formatting to it for backup use. (Basically adding encryption, as I recall.) Now it should be able to make backups to that drive.

NOTE: Once you point to that drive for TM, it cannot be used for anything else because TM now marks it as being ONLY for TM. If that is not what you want, let us know and there are things to do that can make at least part of the drive still available to you.

 

[badshoehabit]

Thank you. Straightforward instructions - but still won't recognise drive.

 

[MacInWin]

I don't understand your screenshot. The target drive is in the left sidebar and looks to be attached, but why are you highlighting "Back up" instead?

Before trying to assign it to TM, can you open the drive in Finder?