Match & replace the elements in a dataset

somewhat similarly to Replace Elements in a Dataset by rules, I'd like to replace the components in all columns named "microseconds" in a hierarchical dataset, with their respective quantity. Something like:

Replace[ myDataSet, Rule["microseconds", x_Integer] -> Rule["microseconds", Quantity[x, "Microseconds"], All]

My attempt (using initial input from @Tomi answer):

ds = Dataset[AssociationThread[{"Data 1", "Data 2", "Microseconds"} -> #] & /@
Table[{RandomReal[], RandomReal[], RandomReal[]}, {i, 1, 10}]]

Now to change "Microseconds" column we apply appropriate function to it:

ds[All, {"Microseconds" -> (Quantity[#, "Microseconds"] &)}]

I'm a little confused as to what you are looking for. But lets say your data looks like:

(* make fake data *)

mydataset =
Table[{RandomReal[], RandomReal[], RandomReal[]}, {i, 1, 10}];
mydataset = Prepend[mydataset, {"Data 1", "Data 2", "Microseconds"}];
MatrixForm[mydataset]

We could do something like

mydataset[[2 ;;, {3}]] =
Quantity[#, "Microseconds"] & /@ mydataset[[2 ;;, {3}]]

What I'm doing here is selecting all values from the second line to the last line, and then the {3}rd column. I then use Map (aka &/@) to apply the function Quantity[] to this dataset, and this results in:

Replace the UnitConvert with Quantity if the column is not already a Quantity.

SeedRandom[123];
RandomSample[ResourceData["Sample Data: Titanic Survival"], 10][All,
<|#, "Age" -> UnitConvert[#Age, "Microseconds"]|> &]

I think I solved my issue with KeyValuePattern

The final expression becomes:

ds[Replace[ #,
match : KeyValuePattern["microseconds" -> t_] :>
Append[ KeyDrop[match, "microseconds"],
"microseconds" ->  Quantity[t, "Microseconds"]], All ] &]