1) download the full installer for 10.13.6 from the Mac App Store and open it to upgrade to MP51.0089.B00.
2) download the full installer for Mojave DP11/PB10 and open it to upgrade from MP51.0089.B00 to 138.0.0.0.0
Yes - thank's very much
See updated specs below (in Dutch):
Hardware Summary:
Modelnaam: Mac Pro
Modelaanduiding: MacPro5,1
Processornaam: 6-Core Intel Xeon
Processorsnelheid: 3,06 GHz
Aantal processors: 2
Totale aantal cores: 12
L2-cache (per core): 256 KB
L3-cache (per processor): 12 MB
Geheugen: 48 GB
Opstart-ROM-versie: 138.0.0.0.0
SMC-versie (systeem): 1.39f11
SMC-versie (processorlade): 1.39f11
Serienummer (systeem): C07JK033F4MD
Serienummer (processorlade): J5240009KBH8C
Hardware-UUID: A5C8E0AD-D62D-599A-A856-9845A5C8D822
PCI:
AMD Radeon HD 7950:
Naam: ATY,Hamachi
Type: Beeldschermcontroller
Besturingsbestand geïnstalleerd: Ja
MSI: Ja
Bus: PCI
Sleuf: Slot-1
Fabrikantcode: 0x1002
Apparaatcode: 0x679a
Fabrikantcode subsysteem: 0x103c
Subsysteemcode: 0x6617
Revisiecode: 0x0000
Breedte koppeling: x16
Verbindingssnelheid: 5.0 GT/s