HEIC is Apple's proprietary version of the HEIF or High-Efficiency Image File format. This newer file format is intended to be a better way to save your pictures, making your images smaller in terms of data while retaining high quality. HOWEVER, Paragon does not currently accept HEIC images.
To automatically convert a HEIC image to a JPG image when you share/send photos from your iPhone or iPad:
Open the Settings app.
Scroll down to the Transfer to Mac or PC section and choose Automatic.