You can change the Analysis Services mode from Multidimensional Mode to Tabular Mode or vice versa easily by following below steps. I did this on SQL Server Analysis Services 2016 version.
Step 1: Edit msmdsrv.ini file
Go to folder X:\Program Files\Microsoft SQL Server\MSAS13.MSSQLSERVER\OLAP\Config
Change X: with your correct installation drive.
Open file msmdsrv.ini in notepad
It is recommended to take a backup first. There is a chance this folder require additional permission to edit so I would suggest you to open the file “as Administrator”
Find the tag <DeploymentMode>0</DeploymentMode>
If your current mode is Multidimensional then the DeploymentMode value will be 0 or if Tabular, then it will be 2. Change it to 0 or 2 as per your requirement.
Step 2: Restart SSAS
Open SQL Server Configuration Manager from Start menu and
Right click on “SQL Server Analysis Services” and click “Restart” in the context menu.
Finished! Try connecting to SSAS instance in SSMS to test.