There are a number of different ways to export file attachments from Survey123. To export individual files from a survey, see the Working with your Survey123 Photos blog post by James Tedrick, Survey123 Product Manager.
If you need to export more than one survey attachment at a time you will need to:
- Install ArcGIS Pro desktop software
- Speak to your Program Specialist about getting access to ArcGIS Pro
- Export a file geodatabase (FGDB) of the feature layer that has the attachments you want to work with. See how to Export data from hosted feature layers
- Install and run the ExportAttachments tool according to the steps found in How To: Batch export attachments from a feature class in ArcGIS Pro