Help Exporting photos in DNG from Lightroom in my iphone

[maofilm1]

I have an iphone 8 with the free lightroom app v.5.2.1 EC3810.

Took  photos thru the lightroom app and I want to export them in DNG format to my computer but I have only been able tot export them in jpg. The photos seem to weight 21 GB and every time I try it tells me I don't have enough memory.  I believe it dosen't work as I haven't paid for the program and I am only using the free version but I want too make sure before I buy it.  Should I download also the lightroom in my computer ?  I am just learning this so I appreciate your opinions.

Thanks

Mauricio

[Jao vdL]

Assuming your images are actually dng or other raw originals (you can't export jpeg or HEIC to dng as there is no point to do that), you accomplish this by choosing "export as" in the export field and then selecting original or "DNG" and then putting it where you want, or by hitting the tiny little preferences icon next to the camera roll option or export to files option:

 

and selecting DNG in the options you get.