It is hard to give a direct answer because you haven't mentioned what type of internship are you looking for. For web developer internship, you should first learn HTML, CSS and JS. After that you should learn some frameworks such as React.js, Angular or Vue. For the server side, you can learn either node.js, spring boot, .net etc. However the most important thing is to build a portfolio. Build projects that solve real problems. Recruiters find it very impressive.
