Hello @Tooba_Aftab first of all buying .com domain is a great decision from your side because that is necessary to show that we are truly interested in our business.
Secondly, you need a .com domain name and hosting to built your own custom website whether it is on WordPress or Blogger CMS.
It is totally depends on your current condition, if your blog has hundreds of web pages OR you are not familiar with technical stuff how to migrate or change permalinks structure inside your blogs etc then would suggest you to upgrade your current WordPress hosting account to premium which contains all premium hosting services features and should be able to mange your business level domains easily.
Yes Right now your domain is looks like WordPress subdomain (test.wordpress.com) which is not acceptable on any hosting service providers, the only thing you can do is register a new domain name with this hosting company and start work on it, further you can transfer your old web content to new one. As far I know free WordPress has no migration tool so that can be the complex part for you because I think that can only be done manually.
We recommend HosterDay hosting services due to their performance and fast speed. Their dedicated technical team is user friendly and fast. I hope their technical team can help you in this concern, you need to send an email at Support[at]Hosterday[dot]com with your queries and requirements.