macOS update fail with recovery start up problems

Tried to update macOS on my iMac and without time machine backup, agh.

Black screen with thunderbolts then folder with question mark.

Start up in recovery but Reinstall shows no disk to select.

Disk utility SSD SM0128G Media shows unformatted and no volumes beneath and I found old link here (Cordovaii) suggesting to partition this with name Macintosh and to format, but don’t know how much to partition?all of it.

I have photos which I don’t want to lose and really concerned.

Help very much appreciated.