Full reset of my M8: Help!!!

Hi Guys,

My M8 was rooted a while back so I'm on an old Android version. I recently upgraded my phone and want to reset my old one for my wife to use... but I honestly can't figure out what to do. I want to get it back to standard build so she can get OTA updates etc and get fully updated.

Can someone help with a description of the steps I need to make - and how exactly I can figure out the correct stock rom to use etc? More than willing to send a few $$$ to someone by way of a thanks.

It's S/Off and here's the config from Fastboot:

INFOversion: 0.5
INFOversion-bootloader: 3.19.0.0000
INFOversion-baseband: 1.21.21331147A1.19_2G
INFOversion-cpld: None
INFOversion-microp: None
INFOversion-main: 3.28.401.6
INFOversion-misc: PVT SHIP S-OFF
INFOimei2: Not Support
INFOmeid: 00000000000000
INFOproduct: m8_ul
INFOplatform: hTCBmsm8974
INFOmodelid: 0P6B10000
INFOcidnum: 11111111
INFObattery-status: good
INFObattery-voltage: 0mV
INFOpartition-layout: Generic
INFOsecurity: off
INFObuild-mode: SHIP
INFOboot-mode: FASTBOOT
INFOcommitno-bootloader: df77f8b7
INFOhbootpreupdate: 11
INFOgencheckpt: 0