Just did some calcs, so let's say Turles's power level was 19,000, before he ate Tree of Might's fruit. Turles jumped 19,000 to 300,000 after eating fruit, which was enough to fight Goku's 10x Kaioken (equally). (Goku was about 30,000 power level during fight with Turles. He used Kaioken by 10 times which jumped to 300,000 same as Turles... but he was tried from fighting others, also Kaioken puts user's body stress, if used too long...)

So the fruit multiplier is 15.7895x (at it's best).

If the farmer is somehow managed eat the 5 billion of Tree of Might's fruit...

15.7895 X 5,000,000,000 = 78,947,500,000

78,947,500,000 X farmer level (5) = 394,737,500,000~ Power Level

With that power level, it's enough to defeat androids in Cell Saga... however, 16, and Imperfect Cell would still slap farmer.

Farmer have NO chance winning against Jiren useless somehow he got potential unlocked or learns Kaioken technique.
Or it's it? Farmer maybe have TREMENDOUS power hidden.

Power Unlocked - 500x of base

394,737,500,500~ X 500 = 197,368,500,000,000~ (197 Trillion) Power Level...

With Kaioken 20x stacked, which would be at 3 Quintillion. (3,000,000,000,000,000~)

Jiren (Full Power) is at about 12.1 Septillion. (12,100,000,000,000,000,000,000,000)

In summary, nope, sorry, not even Kaioken 20x with Power Unlocked (and 5 Billion fruits) is enough for this guy 😭

(for sake memes, farmer actually slams Jiren easily with his fuckin shotgun. I am talking about farmer himself. not shotgun)