You need to get your head around input resolution and output resolution - slides are small, pints are big.
Working backwards then, 250-300 ppi is fine for output, ie printing, you won't see the pixels at that even with your nose on the print.
So at 12" long edge [for A4 roughly] you'll need a file with 3600 pixels long edge [12inches x 300 pixels per inch].
Your actual slide's long edge is only 36mm/ 1.42", so to scan for a 12" print you need to squeeze all those 3600 pixels out of that.
3600pixels/1.42"= 2535 ppi - hence 2900 ppi.
My old slide scanner had a max optical res of 2900 ppi, so I went with that. I would check the max OPTICAL resolution of the scanner and do the same, its unlikely to be more than 4000ppi. A tiff file size of 33Mb sounds about right.