Two ways to estimate
From beats: count your scenes or story units and multiply by pages per beat. One page per beat is brisk, two is typical for a mainstream comic, three suits slow, atmospheric work. From panels: divide the panel count by panels per page. Decompressed storytelling averages about 3.5 panels a page, standard about 5, dense about 6.5.
Add front and back matter (title page, credits, an ad or two) and the tool pads the total to a multiple of four, telling you how many blanks that adds. Once you have a number, check it with the page count validator.