Upgrading Server will I lose data?

unfortunately you will if you use the upgrade feature, as that will create another server rather than just upgrading the one you currently have.

You must use the "change slots" feature to carry out your upgrade. This will remain on the same server, and you will still have saved backup to restore afterwards.

If you're changing slot you wont lose data

if you upgrading hardware you wont lose data (but don't upgrade ram to pro or ultimate as it's not use, its for minecraft server only, Dayz is CPU hog not memory hog)
if you change map from Vanilla to Livonia you will lose data

if you switch server location you will lose data

data is not transferable from 1 server to another server (It can be done by Nitrado support but restoring the backup in such way will not work)