It doesn't matter whether you upload the images in 240 or 300 ppi.

The size/resolution of the image is relevant.

If an image has a resolution of 3000 x 2000 px, it has this resolution - regardless of the ppi.
The ppi only plays a role for the image size when printing.

For offset printing, this means (for an image with 3000 x 2000 px):
At 300 ppi, this would be 25.4 x 16.93 cm.
At 240 ppi it would be 31.75 x 21.17 cm.
Strictly speaking, however, 300 ppi is an old unit from the time when printing was still done in a 60 grid (60 lines per inch / 60 lpi).

Since most printing today is done in 70 or 80 grid, 300 dpi is actually too low.

For perfect image quality with a 70 grid, an image should be switched to 350 ppi. Then you could only print the image with a resolution of 3000 x 2000 px in a size of 21.77 x 14.51 cm.
With an 80 grid, it would only be 19.05 x 12.7 cm, because this would have to be switched to 400 ppi.

However, when it comes to print products that are significantly larger than a book or magazine, such as posters or large-format banners, significantly lower ppi figures are sufficient, as the viewer has a greater distance to the printed matter. Depending on the size, 100 to 150 ppi is sufficient for large posters.

For huge banners that are viewed from many meters away, 60 or 40 ppi may be sufficient.

You're welcome!