I guess LR sees your device as a card reader and will attempt to import all images (usually in a DCIM folder) or from micro SD card if using expandable memory. There are a number of options:
- Import everything (once only) and LR will subsequently import only new photos if you always check the box to exclude suspected duplicates.
- Deselect all and select just the individual items you want to import.
- Copy the photos you want to a folder on your C drive and then use:
Import >> Add (if using this method go to Edit >> Preferences >> General and under import options uncheck the box “Show import dialog when a memory card is detected” and click OK.
I don’t think there is a way to eliminate file types. LR will import all compatible images including PNG.