You have an ERP/ECC system and at present it on EHP4 (SAP_APPL 604). As this is an ECC system you will need to do an EHP update and if you want the NetWeaver level to be at 7.4 you will need to update the system to EHP7 because EHP7 is based on NetWeaver 7.4
SAP versioning, part 2 (why EHP7 contains SAP APPL 6.17)
To go to EHP7 you need to have a supported OS and DB. Check PAM for supported OS and DB combination.
If you update the system to EHP6 then the system will be on 7.31 release.
Why SAP ERP 6.0 EHP6 contains SAP BASIS 7.31
EHP6 and EHP7 need a higher version of OS and DB. Once you have the supported DB you need to create a stack file for the upgrade using the Solution Manager MOPZ and download all the packages for the update and start the update using the SUM tool.
The guides are present at https://websmp208.sap-ag.de/erp-ehp-inst
Reagan