If you always want to insert numbers exactly at position 6, you could generate some rules on the fly like this (attention: with longer numbers and additional insert positions - in addition to position 6 - the rule files could get way too large):
As said if the input and the positions should be much more varying, you probably would need to change to different approaches (including some dictionary splitting/precomputations and/or pipes to hashcat or you need to use other tools from hashcat-utils or use hashcat's stdout option).
Code:
mp64 'i5?d i6?d i7?d i8?d' > insert_numbers_after_6th_pos.rule
hashcat -m 0 -a 0 -w 4 -r insert_numbers_after_6th_pos.rule hashes.txt dict.txtAs said if the input and the positions should be much more varying, you probably would need to change to different approaches (including some dictionary splitting/precomputations and/or pipes to hashcat or you need to use other tools from hashcat-utils or use hashcat's stdout option).