Mobile Application testing is an all-time hot IT job as mobile applications keep evolving every day. when you prepare for this job, it's also important to brush up on your entire software testing skills be it web applications testing, performance testing, security testing.

When they say the position as a mobile tester, they don't just expect candidates with mobile application testing knowledge, they always look for someone who has more experience and knowledge in the testing field. Hence polish up all your knowledge on

1. SDLC/STLC concepts
2. Domains that you have worked
3. Web app, Mobile app, performance, and security testing concepts and automation tools(if any, handled before)
4. Project management tools and defect management tools handled so far
5. Latest Android /iOS versions and their major features

Please feel free to add up if any points are missed above.