import address book without creating a duplicate

hello, I just installed Mint 18.3 and Thunderbird. From my W7 Thunderbird installation, I exported that address book (PAB) as a .csv file with the same name IE: Personal Address Book In the new installation if I choose IMPORT, I end up with two PAB'S showing in T Bird. Luckily T Bird recognizes the duplicate one when I compose mail. I can't delete the original PAB file but I can delete the duplicate. I'm sure I could rename the exported one to something else and it should work......but.... Is there an easy way to get the contacts out of the exported .csv file and into my existing PAB? Clear as mud I guess.. sorry for not being more clear. Thanks, Tinsby