Export:
On the Windows 2003 DHCP server, navigate to a command prompt
Type the following Command: netsh
Type the following Command: DHCP
Type the following Command: server \\Name or IP Address
Type the following Command: export c:\DHCPdb all
Import:
Type the following Command: netsh
Type the following Command: DHCP
Type the following Command: server \\Name or IP Address
Type the following Command: import c:\DHCPdb
Close the command prompt when completed.
Return to DHCP located in the Server Manager dashboard.
Right click the designated DHCP server in the services pane, then select Restart.
Once the DHCP install has been completed, select DHCP located in the Server Manager dashboard
Right click the designated DHCP server in the services pane, then select Stop.
Delete the DHCP.mdb file under c:\windows\system32\DHCP folder.
Return to DHCP located in the Server Manager dashboard
Right click the designated DHCP server in the services pane, then select Start.
source: https://docs.microsoft.com/en-us/archive/blogs/canitpro/step-by-step-migration-of-dhcp-from-windows-server-2003-to-windows-server-2012
