I am travelling from Mauritius to UK for a few days then to Dublin for 3 days. Do I require a visa for Dublin
If you are a Mauritian citizen, then yes you do need a visa to visit Ireland. From Visa policy of Ireland:
Visa policy of Ireland is similar to the visa policy of the Schengen Area. It grants visa-free entry to all Schengen Annex II nationalities, except for Albania, Bosnia and Herzegovina, Colombia, Georgia, Marshall Islands, Mauritius, Micronesia, Moldova, Montenegro, North Macedonia, Palau, Peru, Serbia, Timor-Leste, Ukraine and Venezuela.