Chilean Garin beat Norway's Casper Ruud 6-4 6-4 and then Pella overcame in-form Serbian Laslo Djere 7-6(10) 7-6(1) on Saturday.
Garin is 22 and ranked 92nd in the world, while Argentine Pella is 28 and ranked 44 places higher.
Pella had the harder road to the final on Saturday against Djere, who leapt to 37th in the world after winning his first ATP tour title in Rio last week.
The Argentine won the first set with a hard-fought tie break and opened up a 5-2 advantage in the second but Djere fought back before Pella won out in another tie break.
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(Writing by Andrew Downie; editing by Clare Fallon)
