I am assuming you are talking about Adobe Fresco here.
If you want to open a project on Fresco, it will show PSD files as only PSD files are readable by Fresco (Psdc - or PSDCloud files are the app native file format)
If you want to create a new project from scratch at a specific size, you need to know the size before hand, unless Fresco can open it and lets you check the size before closing and creating a new one again (or you're OK to duplicate this file and use the copy to create a new artwork)
If you're working on a Windows machine, you can still check the image size by right clicking on the file and checking properties

(ALT+enter)
then "details"

I don't think that's possible that easily on an Ipad...