New column in table that populates based on another table

Hi everyone,

I'll try to be as clear as possible:

I'm working on some data in which each observation is a single transaction ID (about 30000 observations). There's variables for location (province theres about 100 of them) and for type of event. I have a separate table in my model that corresponds population to each province.

What I want to do is to add a new column to the main table (the one that contains every single observation) that populates based on population for the respective province.

Is my only solution to write a neverending ifelse function in DAX that does this or is there a more elegant and simple solution?

Edit:

I'm including a sample data set with randomized values, as suggested by ams1 (thanks!):

Table with transaction ID and geographical info

Reference table with population per province:

Thanks in advance!