I wonder if each cell possess only one strand of DNA which according to my book is more than "7 feet" long(if uncoiled), then why does human has 46 chromosomes which are actually coiled chromatin (DNA wrapped around histone proteins)? Does DNA break into parts and form 46 chromosomes during cell division (I am just guessing I am not sure about it)?
Human cells contain 23 pairs of chromosomes (46 chromosomes in total). Each chromosome is formed by 2 strands of DNA tied by hydrogen bonds to each other making the classic DNA double helix (double-stranded DNA). So, in total there are 46*2=92 strands of DNA in each diploid human cell! Gametes contain half of the chromosomes, so half of the strands as well.
Each chromosome is present twice in every cell (excluding sperm and eggs, where only one of each is acquired in meiosis). So yes, that is 46 'strands' of DNA wrapped around histones as you said.
During mitosis each chromatid is replicated, and then in anaphase the sister chromatids are separated in to each daughter cell.
Any basic high school/university text book will have a good diagram of this.