As an android apps developer, I don't have any idea of the design but I'm looking to design my game like this type of design.
Can I know what is the name of these types of design?
So you are searching for tutorials?
Yes, I'll try with myself first, But If I find it hard so I'll hire people to do that.
I don't think there's a specific name for that style.
It has some handdrawn chldrens' book quality to it. So you would want to look for illustrators that can do illustration for childrens' media and are aware of interface design needs. And this needs to be vector artwork. It would help that you post links to examples when posting your job offer.
It might get tricky to find someone.
Depending on whether you want to use SVG files in your app and whether you want to script or animate these files, you might need to make it very clear that the artwork has to be created in a vector application and not just autotraced. And that perhaps additional requirements mgith need to be made (for making illustrations interactive or for animating them).