How can you iterate through a dictionary and change every value?

I have a dictionary for strings and floatrs,

    public Dictionary<string, float> StockNames = new Dictionary<string, float>();
 void Start(){
        StockNames.Add("ChickenNFries_S", 68.41f);

        foreach (string v in StockNames.Keys)

Then that to iterate through which works. However, you cannot directly change the variable through the iteration as it errors out. I tried to throw another function in there which would be called each iteration

IE changeValue(v)

but that errored as well not allowing me to change them, leaving the only way I know how by literally typing in each name StockNames[“ChickenSFries_S”] = 2.0f; Isn’t there a way to iterate through them all and set them as you go?

You can get a collection of all the values (Dictionary<TKey,TValue>.Values Property (System.Collections.Generic) | Microsoft Learn), but I dont think that will help with non-reference types like float.
You could get the collection of all keys (Dictionary<TKey,TValue>.Keys Property (System.Collections.Generic) | Microsoft Learn), then loop through that to get your dictionary indexes.
e.g. (uncompiled example)

Dictionary<string, float> StockNames = new Dictionary<string, float>();
//... dic intilization stuff...
Dictionary<string, float>.KeyCollection keys = StockNames.Keys;
foreach (string s in keys)
   StockNames ~~= 68.234f;~~