Where did Alfred the great grow up?

Camelot. It says so in all of the stories. He built a castle at Camelot and lived there.

There is no easy answer to this question. First, it is bound up in the question of whether or not King Arthur really existed; then, you have to consider, if he did exist, who was he?

If Arthur was a Roman Briton, that might place him in a very different time period than if he was a Welsh warlord. Since there is very little direct evidence for Arthur's existence, we basically have to pick our favorite theory and make assumptions based on that theory.

We can narrow down the Arthurian time period, however. Most of the time, in movies and television shows and in many books, Arthur is depicted as a king in plate armor living in a grand castle, which places him more or less in the high Middle Ages. This is about seven hundred or so years after any of the possible King Arthurs would have lived. The Arthurian era settles around the year 500 AD. We can't know if that was the year he was born, or the year he died, or the year he fought the Battle of Badon, or the year he married, but various early accounts of Arthur pinpoint events in the decades before and after 500 AD.

Whether or not Arthur was a real person (and this is a matter of considerable doubt) we can make some statements about where he lived, or supposedly lived. Certainly in the British Isles, and certainly not in Ireland or Scotland. Probably in Wales, south-western England or central England. This was during the dark ages, and there is almost no written history of the period from the period. Almost everything that we "know" about Arthur was written a lot later, and much of it is admittedly fiction.

2 places i know King Arthur once lived, if he did exist, was Cadbury Castle, and Tintagel Castle, both of them were in England, but now lay in ruins.

a long time ago .

The above does not answer the question. King Arthur is supposed to have lived in the west of Britain, chiefly in the part now called Cornwall. He is a legendary figure, nobody can actually prove that he existed.