Paint can separate the background of an image if that background consists of a solid color. You can then paste this background into another image. However, it cannot save an image with a transparent background. All transparent parts of the image will be replaced with white in the saved image. On the other hand, you can create a real transparent background with Paint 3D (it is in Windows 10) or with Gimp, which is free software.
Steps

Step 1. Open your image
Right click on your image and position your cursor on Open with, then select Paint in the list of programs.
The image should have a solid or white background

Step 2. Select the background color
Click Color 2 in the toolbar at the top of the window. This is where you can select your image background color as Color 2.
- For example, if the background of your image is white, you need to adjust Color 2 on the same shade of white.

Step 3. Take the selection tool
Click on the eyedropper in the toolbar.

Step 4. Click in the background
This will set Color 2 to your background color. Now you can separate your image from its background.

Step 5. Open the Selection menu
Click Select on the toolbar. A drop-down menu will appear.

Step 6. Click Transparent Selection
By doing this, you enable transparent selection for all of your selections. A check mark will appear next to the option in the menu.

Step 7. Choose the type of selection
Click Rectangular Selection or Free Selection. You will find these options in the menu To select.
- Depending on the area you want to select, you can use either of these tools in the mode. Transparent selection.

Step 8. Select the image
Choose the image you want to separate from the background and draw a path around it.
You will see a black outline appear, but it will disappear when you release the mouse button

Step 9. Display the selection
Right click in the selected area. You will then see a dotted rectangle appear.

Step 10. Copy the selection
Select Cut or Copy from the context menu. This will copy the selection to the Clipboard.
This will separate the image path and the background

Step 11. Open a new image
Click on File, then New, this will open a new image. You can now paste the image you just copied there.

Step 12. Paste your image
Right click on the new image and select To stick on. This will paste the image, which you previously copied or cut, into the new image with its old background which is now transparent.