@ItzZia: The SD card will need to be formatted for use with your Galaxy Note 20 Ultra, therefore please backup any existing data on the card before proceeding with the steps below.
With the SD card inserted, go to Settings > Battery and device care > Storage > Tap the 3 dots in the top right > Advanced > SD card > Format
Your device is compatible with micro SD cards up to 1TB capacity, which can be used to store personal files and media, but not applications and their associated data (in most instances). To set the SD card as your default storage location for photos and videos captured via the Camera app, please open the Camera app > Tap the cog symbol in the top right > Storage location > SD card.
To move files to the SD card, please swipe up from your Home screen > Samsung (folder) > My Files > Images (as an example) > Press and hold on an image, then tap any others you'd like to move (or hit 'All' in the top left) > Move > Back > SD Card > Select a folder, or create a new one > Move here.