//If you want to iterate over a Map and do some logic for specific keys use this

Map<Integer, String> m= new Map<Integer, String> {1=> 'a', 2=>'b'}; Integer[] n = new Integer[]{}; for (Integer i : m.keySet()) { n.add(i); } Integer j = 0; for (String s : m.values()) {
if (n[j]== 1) { // 1 here is value of the key, you can use your value

        //DO something
        system.debug(n[j]+' '+s);    j++;
    }
}

If you want to iterate over a Map and do some logic for specific keys use this

Map<Integer, String> m= new Map<Integer, String> {1=> 'a', 2=>'b'};

Integer[] n = new Integer[]{};
for (Integer i : m.keySet())
{
    n.add(i);
}
Integer j = 0;
for (String s : m.values())
{        
    if (n[j]== 1) {  // 1 here is value of the key, you can use your value
    
        //DO something
        system.debug(n[j]+' '+s);    j++;
    }
}