Sum 2 columns

Hello,

Is there any way to make one column from 2 columns. So their values are just add to the new column with ‘-’ between them?

So I have a column with the year its all 2024 and there is a column which are the month and I want to merge that two columns and the merged column values should look like this : 2024-1

After that I need to put -1 to every cell in that column so at the end it should look like this: 2024-1-1

Here I want to merge the LETO and the MESEC column

Thanks!