Bolt Size for Seat Frame?

[HRTKD]

I added sound insulating panels and new carpet to the floor. I don't think the old bolts that hold the seat frame to the floor are going to be long enough now. Can anyone tell me what size bolts these are? The helpful hardware man at Ace Hardware couldn't come up with the right one. But I might have got him on the wrong track telling him it was from a '91 Ford so I think he only checked SAE size bolts. Could it be a metric size instead?

 

[HRTKD]

The bolt size was metric. I don't remember the exact size though. Sorry.