Create a column date from 12 months columns

Hello guys, I 've this kind of situation:

I'd like to play with budget, which was made in an excel, 12 columns (1 per month) plus other data (category etc). How could I tell powerbi to consider those columns in a sort of unique big "pivot" so I could create time series?

I 've said pivot because in Tableau, pivotting those columns all together, provide the result I'm looking for but I wasn't able to perform the same trick here. 

As an expaple, my db looks like this (gennaio stands from January and so on): 

I 'd like to create this time serie whatever because I want to compare actual data vs this budget data, combine them, forecasting etc...

any idea? 

Thank you!