First, this is the. AE forum and not the Lightroom forum... but that's okay, welcome aboard.
Second a dire warning. -- DO NOT ATTEMPT TO USE AFTER EFFECTS WITHOUT LEARNING THE BASICS. Failure to do so will result in failure & frustration. Go to the Adobe web site and search for the Getting Started With After Effects page. You need that stuff before you launch off into the fun stuff.
But to answer the initial query, you can import a series of stills into AE as an image sequence--far more than 99.
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