Try this eBook Cover Creator - Design Your Own 3D eCover online
They have a free option but it only has limited book cover types
I use the paid version all the time and it produces great book covers in 3D
Cheers
Mark

Adobe Photoshop is a free apps, If you have the knowledge to operate the apps, you will be able to make the cover at a free of cost. Here you can get the Idea by the help of search engine. You will be able to see many sample cover. then you need to follow the sample cover. Thanks

What's your design experience and graphical limitations?

Do you have the knowledge/ability to do this yourself or are you looking for a tool to do it all for you?

You can use this one to make your ecover http://ecover.onlineecovercreator.com/
I use this site from time to time and it's actually quite easy to create a ecover in a couple of minutes!

Fiverr is a good place to look if you wanted to convert your 2D cover into 3D

Make sure you look at the reviews and samples before choosing.

I do offer this service on fiverr too but i would still recommend having a look around

[DELETED]