Slóthi is worried that when the Orcs attack, the dwarves might be cut off from the outside world and will not survive a long siege.
'Bósi has tried to keep it quiet, but rumour travels quickly in the passages of Moria. Most of us are now aware of Balin's end. They were surrounded: Orcs from the east and below, and the terrible creature in the pool by the Hollin Gate.
'We cannot afford for that to happen again, ${PLAYER}, but if it does, it is my responsibility to make sure that we have enough supplies to withstand a long siege.
'I want you to leave Moria and speak to Thórgnyr just outside the Doors of Durin; tell him to send us as much food as he has to spare and to arrange for more on a regular schedule. We will not be put in the same dire place as Balin's company. I would see us avenge them so they may then rest in long peace beneath the stones.'
Thórgnyr is outside Moria by the Doors of Durin before the still pool.
Slóthi wants to ensure that the supply route outside Moria remains open and that there is enough food within the mines for the dwarves to survive a long siege.
Slóthi is in the Chamber of the Cross-roads, at the southern entrance of Durin's Way, north of the Great Delving.
Thórgnyr has given you the first of several food deliveries for Slóthi, who can be found in the Chamber of the Cross-roads.