I want to allow camera settings in this site only

Hello!

Go to the website where you want to allow the camera. Click the lock icon in the address bar (left side). Click Permissions (or More Information → Permissions depending on your version). Find Camera in the list. Select Allow for this site. Reload the page so the change takes effect.

Hope this helps!!

When you first visit a website that requests camera access, Firefox will show a pop-up prompt to select.

IF you already accept that

You can manage all your saved camera permissions from the settings menu.

Click the menu > Settings > Privacy & Security > Scroll down to the Permissions section, find the Camera Settings...

This will open a list of all websites with saved camera permissions.

Find the website you want to grant access to and use the drop-down menu next to it to select Allow.

Click Save Changes.

For more info please read that article

https://support.mozilla.org/en-US/kb/how-manage-your-camera-and-microphone-permissions#:~:text=Change%20camera%20permissions,-In%20the%20Menu&text=Scroll%20down%20to%20the%20Permissions,change%20permission%20for%20the%20website.