For only photo editing, will monthly $9.99 be good?

PS file ending is post script, not photoshop. Photoshop files and with psd or psb. If the Lightroom application still works, before subscribing to photoshop, make sure your file type association is correct. You may be able to associate all compatible files in Lightroom’s preferences. To manually associate, if you’re on a Mac, right-click (or ctrl + click) on one of the files you used to open with Lightroom and select Get Info. Find in the info window where it says Open with.... and make sure it says Lightroom. Click the button that is labeled Change All... to make all files of that type open with Lightroom. Something similar for Windows should be found in a tutorial on YouTube. This should work if Lightroom still works and your files have not had their extensions changed by some other software install.