Hi Gary,
By default, the screenshots are saved in the C:\Users<user name>\Pictures\Screenshots directory. To change the save location in a Windows 10 device, right-click on the Screenshots folder, select Properties & select the Location tab then you can relocate it to another folder if you want to. For more information, see Capturing screen contents - the PrntScrn key, Win-Shift-S, the Snipping tool & Screenshots by Tryx3.
Changing the default screenshot file type to .GIF would not be possible unless you change the file type before saving it.
Let us know if you need further assistance.
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