First of all, your formula is not very reasonable. You need to change it to this

=IF(ISNA(VLOOKUP(E8,[Transfer.xls]Xiamen January computer subsidy!$C:$ H,6,0)),"",VLOOKUP(E8,[Transfer.xls]Xiamen computer subsidy in January!$C:$H,6,0))

It means cell E8 For the value, search in the ?[Transfer.xls] Xiamen January Computer Subsidy? in the 6th column of the C:H column in this worksheet, that is, column H. If it cannot be found, it will display "" (that is, nothing Display), otherwise the value found by the VLOOKUP function is displayed.

Attached is an example diagram of the use of the VLOOKUP function and the IF function, which will make it easier to explain the usage of these two functions. I hope it can help you.

IF function usage