OS El Capitan v10.11.6 upgrade to OS Mojave 10.14.16
I have a Mac Air (mid 2013) current OS El Capitan v10.11.6 and want to upgrade to OS Mojave 10.14.16. I have read a previous post circa 2018 which advised to download Mojave via the App Store. The App Store is now different and does seem to have link to Mojave. I have found another route to do this but it results in an error message stating the 'download file is corrupted'. I also have a Mojave download file on USB which I have used successfully on another Mac updating from High Sierra but when I tried on this computer got the same error message. Ideas/suggestions please.
MacBook Air