You are givin these missions by TANNIS at Tartarus Station. Are You From These Parts?
The first one asks you to collect 6 Claptrap parts, these are marked. Fight For Your Right To Part-E
The next mission asks you to obtain 42 parts,Parts Is Parts
The next mission asks you to obtain 75 parts,We All Have Our Part To Play
The next mission asks you to obtain 100 parts,A Part Of Something Larger Than Yourself
The final mission asks you to obtain 150 parts.
These parts can be farmed in the Hyperion Dump, North of where you obtain the quests. You can farm these parts by killing claptraps that spawn in the dump. When you run out of claptraps, save and exit and start again in the area as all the claptraps will spawn again. It’s a grind and one of the worst mission series in the game.. :/
For more information on these quests please see - https://borderlands.fandom.com/wiki/Tartarus_Station_Mission...