Can someone tell me how to open sldr files in shapr3d
Just like any other file in any other app, you can use the native share menu in yhe files app for example. https://support.shapr3d.com/hc/en-us/articles/115002430653-How-do-I-import-files-from-third-party-apps-into-Shapr3D-
The other way is to tap on the import button in your workspace, and open the file from there.
Another option is to create a new workspace, there you have two options: new design, or create new desing from imported file.