in a paragraph field i will provide input as
test1
test2
test3
How this data will be stored in db ,is it will be in line by line as separate string or as a single string
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If you're entering them all into a single text value like from a paragraph field, then unless you do something additional to that text value, it will all be stored together in one text value of whatever database column you write it to. It's impossible for anyone here to tell you what to do when you don't tell us about what your requirement is, what you're hoping to do with it, etc. Do you have a more experienced appian developer on your team you could talk about this with?
Also, once again it's not necessary to make a new thread for every part of the same related subject - this is the third one so far that's related to the same original question, when you could just follow up with other replies on your existing post(s).