Describe the works of Saint Patrick in the 400's.

a shorter better answer would be

In the 400's, Saint Patrick converted many people in Britain and Ireland.

Saint Patrick (in Latin: Patricius) was a Christian missionary and is known as the patron saint of Ireland, along with Saint Brigida and Saint Columba. He was a preacher and religious of Britannia, traditionally considered the introducer of the Christian religion in Ireland.

Traditionally, based on stories invented centuries later by Christian monks, it is associated with having used the three-leafed shamrock (Trifolium dubium), now the official symbol of Ireland, as a metaphor to explain the Holy Trinity. Likewise, he is credited with the feat of having rid the island of snakes.

When Patricio was still a teenager, at the age of about 16, he was taken prisoner during a Scots pirate raid, which also meant the destruction of the family home, being taken to Ireland and enslaved. In his writings he only mentions a place name that allows locating the area where he lived in Ireland: silva Flocuti, that is, the 'Flocut forest', located near the 'western sea'

Patricio ended up becoming a preacher of the Gospel in Ireland, an island that at that time was divided into numerous clans subject to the powerful authority of the Druids. It adapted very well to the social conditions of the place, forming a local clergy and several Christian communities, respecting the traditions and customs of its inhabitants. He is known as the Apostle of Ireland, where he died about the year 461 of old age.