Try loading the dll using Add-Type like so:
Add-Type -AssemblyName "Microsoft.SqlServer.Dmf.Common, Version=13.0.0.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91"
It will check in the current directory for the dll, unless it's already been successfully loaded previously.
If you still get not found, the version of Microsoft.SqlServer.Dmf.Common.dll in the folder is not the dll needed by the IntegrationServices assembly.
To check the signature of the dll in the current folder, you can run:
([System.Reflection.Assembly]::LoadFile((Get-Item ".Microsoft.SqlServer.Dmf.Common.dll").FullName)).FullName
Notes to help locate matching dlls.
12.0 = SQL Server 2014
13.0 = SQL Server 2016
14.0 = SQL Server 2017
Alternate Option:
In the case below, I'll initially load IntegrationServices "Version 14.0.0..." so that the dll doesn't need to be manually loaded from file or added to GAC.
C:>attrib /s gacutil.exe
A C:Program Files (x86)Microsoft SDKsWindowsv10.0AinNETFX 4.6.1 Toolsx64gacutil.exe
A C:Program Files (x86)Microsoft SDKsWindowsv10.0AinNETFX 4.6.1 Toolsgacutil.exe
A C:Program Files (x86)Microsoft SDKsWindowsv7.0ABinx64gacutil.exe
A C:Program Files (x86)Microsoft SDKsWindowsv7.0ABingacutil.exe
A C:Program Files (x86)Microsoft SDKsWindowsv8.1AinNETFX 4.5.1 Toolsx64gacutil.exe
A C:Program Files (x86)Microsoft SDKsWindowsv8.1AinNETFX 4.5.1 Toolsgacutil.exe
C:>cd "C:Program Files (x86)Microsoft SDKsWindowsv7.0ABinx64"
C:Program Files (x86)Microsoft SDKsWindowsv7.0ABinx64>gacutil /l | find "IntegrationServices,"
Microsoft.SqlServer.Management.IntegrationServices, Version=11.0.0.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91, processorArchitecture=MSIL
Microsoft.SqlServer.Management.IntegrationServices, Version=12.0.0.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91, processorArchitecture=MSIL
Microsoft.SqlServer.Management.IntegrationServices, Version=13.0.0.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91, processorArchitecture=MSIL
Microsoft.SqlServer.Management.IntegrationServices, Version=14.0.0.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91, processorArchitecture=MSIL
C:Program Files (x86)Microsoft SDKsWindowsv7.0ABinx64>gacutil /l | find "Dmf.Common,"
Microsoft.SqlServer.Dmf.Common, Version=14.0.0.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91, processorArchitecture=MSIL
C:Program Files (x86)Microsoft SDKsWindowsv7.0ABinx64>gacutil /l | find "Dmf,"
Microsoft.SqlServer.Dmf, Version=12.0.0.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91, processorArchitecture=MSIL
Microsoft.SqlServer.Dmf, Version=14.0.0.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91, processorArchitecture=MSIL
C:Program Files (x86)Microsoft SDKsWindowsv7.0ABinx64>