Translation:I used to get money on Friday but now I get money on Monday.
In league with our commonly spoken English, this would directly translate to 'the Friday' and 'the Monday'. This is to reference a specific, regular occurance. There has been a regular issue with direct translation versus common interpretation across the site but this is one instance where (as an Irish person) it was especially confusing to remove the 'the' from the English translation.
I think the meaning is "every Friday" or "most Fridays", so my preference would be for, "I used to get money on Fridays, but now I get money on Mondays". It makes more sense to me to translate "on Friday" as Dé hAoine and "on Monday" as Dé Luain, but I'm happy to be corrected.
While superficially similar in outcome, "I get paid" and "I get money" are grammatically very different sentences. "paid" is a past participle, and "money" is a noun, and "I get paid" is a sentence in the passive voice - "I" is not the "actor", the person performing the verb. (The passive voice is often defined in tems of the verb "to be", but "to get" is also used for certain verbs in the passive voice).
In Irish, you use the saorbhriathar to say "I get paid".
Íoctar ar an Aoine mé - "I am paid on Friday(s)" (every Friday)
Íocadh ar an Aoine mé - "I was paid on Friday" (once, last Friday)
D'íoctaí ar an Aoine mé - "I used to be/get paid on Friday(s)" (every Friday).
You can see that in Irish, the distinction between the 1st person active voice sentence D'fhaighinn airgead ar an Aoine and the saorbhriathar D'íoctaí ar an Aoine mé is far more obvious than in English.
One further technical point. While the saorbhriathar is used to translate many English passive voice statements, the Irish sentence is in the active voice, not the passive voice, because the key feature of a passive voice statement like "I got paid" is that the "actor" is unidentified - it doesn't matter who did the paying. It isn't important whether the "voice" is active or passive, it only matters that the actor is not identified. Not identifying the "actor" is exactly what the saorbhriathar does - mé is not the "subject" of D'íoctaí ar an Aoine mé.