EOS Rebel T7 How to take photos at 300 dpi

[Redsed]

I am just learning how to take photos of my artwork to post on a marketing site. I am told I have to post a min. 300 DPI photo which means I need to change my settings and photograph all my artwork...again.  Can someone give me a simplified explanation about how to do that. Sorry if this sounds a little crazy but I have put myself in a position to learn every. single. thing. about websites and social media and cameras all at once.  If I can just take the right pictures I will be miles ahead of where I am now. There are plenty of tutorials about what to put the setting on when you start out but not what any of those settings actually mean.  Thank you so much for any information. 

[johnrmoyer]

I re-read your question. I hope some of this might be helpful.

It is not clear to me whether you are selling the original art or are selling prints. I had previously guessed you were selling prints and the marketing site was doing the printing.

If selling the original art, then if the work is 20 inches by 30 inches, the photo would need to be 6000 pixels by 9000 pixels to have a 300 dpi digital copy of the original. Depending upon the marketing software, then one might be able to zoom in on the digital image to see brush strokes.

Since the Rebel T7i can produce an image of 6000x4000, if you had no margins this could sample an original art work at 300 dpi for a size up to 20 inches by 13.33 inches in a single image. If cropping margins from the photo or if the original is larger, then it would be necessary to stitch multiple photos together.

One could create a 6000x9000 digital image from photos made by a camera that has less resolution by stitching together multiple photos. I use the free hugin software to stitch images together.