Hi peaches1,
exFAT fornat is not compatible for windows thats why you can't open your files. One option is to reformat your SD Crd to fat32. Please make sure to back up all your data because reformatting your device will erase all your data.
1.)COnnect your device to the computer
2.) Go to computer
3.) To a right click in your SD CARD
4.) Formaat
5.) Choose FAT32 as the type or click RESTORE DEVICE DEFAULTS
6.) Click okay or FOrmat.
Try saving files from your phone then connect it to your computer. Hope this helps!