I have sent you PM with direct links. Note there are 2 revisions of the mixer, V1 and V2.
In general, Behringer/Midas Download page has two tables. In the first you select what you want and in the second you can click on download. Both are not really accessible.
But for Midas MR18 there is faster way, go to the product page
https://www.midasconsoles.com/product.html?modelCode=0605-AAF , Google find it as one of the first when you search,
tab till the list Software, enter to expand, arrow to the software you want, in this case firmware 1.22 for V1 or V2, enter to select. There will be no notification, but a dialog will be presented to agree with the license. Technically it is at the end of tab order, so tab till dialog, select "I agree" in it and then enter on "Download" button.