1 Avoid doing it from the desktop
The first thing to keep in mind is that ensure that you do not do it from your desktop as it might result in losing all your previous like and comments on that picture.
2 Use the Facebook App
Always use the Facebook app if you want to use your old picture for your profile picture. Do it through a mobile device, if you want to keep the likes and comments.
3 Click on your Profile picture and choose 'Choose from photos'
For changing the profile, click on your existing profile picture. After that, select the option which says 'Choose from photos.' Now you will see all the old pictures that you would have uploaded before.
4 Choose the Album you want
Now, you need to select the Album from which you want to get your picture. Once you choose the Album, after that, you can select from the profile pictures album if you wish to use your old profile picture.
5 Choose the picture you want
Once you choose the Album after that, select any image that you want to update to your new profile picture. Once you select the picture, then press enter. (See Why Is Facebook So Addictive?)
6 Click Done in the 'move and scale' step
Now you would get an option to move and scale, adjust the picture as per your choice, and click on the 'Done' option.
7 Check for your comments and likes
Once the picture gets uploaded after that, you can check all your likes and comments would be there on your profile picture. (See Why some people are always online on Facebook?)