Can you help point me where to ask this question?

With the following detail of a document in Archion, referenced in Family Search - does this tell me where the document is? Thanks for steer you can give on this. Regards, Karen.

Source Detailsp127 122
Digital Folder Number102457910
Microfilm Number184966
Originating SystemEASY
Indexing BatchC00583-7
I am sorry, but this is no information or document in Archion.

Did you mean to write Ancestry instead?

When you follow the links you'll see on FamilySearch:

Event PlaceHannover, Hannover, Preußen, Deutschland

Regards, Vera
you find
—> Suche nach:
—> Film-/Fiche-/Aufnahmengruppen-Nummer (DGS)
enter your microfilm number —> 184966
in the opening window (Evangelische Kirche. Apostelkirche Hannover) click
—> Kirchenbuch, 1884-1934
and you’ll see the first entry
—> Taufen 1884-1887 (film #) 184966 (DGS #) 102457910

Hope that helps
Should your question eventually refer to a Matthes (which I trust since even the page number is identical to your initial quote!!), then you may i.e. find on FamilySearch

NameJohannes Friedrich Heinrich Matthes
Birth Date16 Nov 1885
Father's NameFriedrich Otto Matthes
Father's SexMale
Mother's NameMathilde Berthe Lucie Matthes
Mother's AliasZöllner
Mother's SexFemale
Mother Is MarriedY
Event TypeBaptism
Event Date14 Mar 1886
Event PlaceHannover, Hannover, Preußen, Deutschland
Page Number127;127
Affiliate NameEvangelisches Kirchenbuchamt Hannover
Church NameEvangelische Kirche. Apostelkirche Hannover
NoteTaufen 1884-1887
....or this Matthes family tree on FamilySearch

Thank you so much for this. I think I need to reinstate my membership of Ancestry to see this document however. Which is annoying because I am sure that ultimately it is a Church Document in your records. Thanks for the help though! Karen.
You already learned that the desired records are in the church registers

Apostelkirche Hannover

When you search Archion’s holdings for that church, you‘ll come up with Zero results.

The Apostelkirche was founded in May 1884, as a now independent part of the

Christus Kirche Hannover

….as i.e. described here

When you again search Archion for that church = Christus Kirche, you’ll come up with this

That said as you can verify yourself, the desired records are not available on Archion. (Taufen / Baptisms are at this very monment only available on Archion until 1875!)
Sorry. Vera