How to change my settings to default factory settings on m Nikon d3000?

I'm new with this camera so I was playing with the settings and I really ****** them up…

Check your owner's manual for instruction on how to reset the camera's setting to how it came from the factory. I think it's on pg 155.

In the future, only make one change at a time in the settings in the camera menu and take some test shots.

If you shoot in RAW, then you will be able to processes those image files in Lightroom CC and make any changes there which can be reversed, all or none because the RAW image files are NOT changed, only a record of those changes are kept as a "sidecar" XMP file associated with the original RAW image file.

When you export those changes as a JPEG image file, any changes you made in LR CC will be reflected in those images

Look on pages 119 and 125 of your user manual to learn how to reset your camera settings

It's in the Menu on your camera.

Read the manual.

IF you're talking about exposure settings though, just set the mode dial, ISO and white balance to Auto then make sure exposure compensation is zero.