It would have been impossible for President Trump to know about Konstantin Kilimnik being a Russian spy before pardoning Paul Manafort, because according to an April 16, 2021 NBC news article "On Thursday the U.S. Treasury sanctioned Kilimnik and
for the first time said he passed along the data to Russian intelligence services."
See U.S. has new intel that Manafort friend Kilimnik gave Trump campaign data to Russia