Converting a File from Illustrator to Photoshop

That is not possible Photoshop is a Pixel editor where Illustrator is a vector editor.  You can place in Illustrator vector files into a Photoshop Document as a vector Smart Object Layer.  Photoshop does not have support for vector files. It can only import them as a single raster layer there will be no vectors in Photoshop for Illustrator vector files. Vectors are in the .SVG and .AI files and supported by vector editors like Illustrator.

Collage and Mockup templates need not be hard to use wit vector images.  However my Photoshop  Photo Collage and Mockup Toolkit's scripts do not support  populating templates with .SVG and AI images,  Though it would be easy to add that support to the Collage scripts for they use Photoshop Place to populate images,  The Batch Mockup Scripts though have a  edit option the opens replacements.  I never tried  to open vector file in Photoshop script for I know Photoshop would switch  from open to some importer, for vector files like .svg and .ai files,  The replace content feature is like Placer vector file would most likely work. 

Photoshop Photo Collage and Mockup Toolkit 

I do not install Illustrator so I tend not to support  .SVG and .AI file for Photoshop does support for vector file types.  Photoshop can use vector file content as a single  raster pixel layer not vector layers. Vector Smart Object Layer Vectors are in the layers object not the Photoshop Layer.