I saw that your question was unanswered now for quite some time, so here is my best shot.
I was in a similar position, implementing IFS for a manufacturer, so not such a different position.
What I did was asking the control body first, what they did was giving me an indepht phone interview, (what we do, how we do it, what kind of machinery and so on), then they told us which exact standard to apply.
Since there are a number of ressources available, you could just decide on the standard (FSSC, IFS, BRC and so on, try and find out what the costumers want and do that, I personally like the FSSC if there are no preferences).
After that you can check the store again, you will have far better information at hand, to choose the right manual.
I hope that is of some help for you.
Edited by Lucas H, 03 April 2020 - 05:26 PM.