Design pattern to use to populate multiple class fields

I have a use case where I have to parse an XML document and fill details in a corresponding fields of an internal model POJO Details. Let's say, the XML look like following -

<?xml version="1.0" encoding="UTF-8"?>

...
<TagA>
 <Child1>
 ...
 </Child1>
 <Child2>
 ...
 </Child2>
</TagA>

...

<TagB>
 <Child1>
 ...
 </Child1>
 <Child2>
 ...
 </Child2>
</TagB>
....

And the internal model POJO looks like following -

public class Details {

...

Set<TagAInfo> tagAInformation; 
Set<TagBInfo> tagBInformation;

...

}

The XML has multiple fields like TagAs, TagBs etc.

Current implementation: So currently there is a mapper/parser class(let's say Mapper.java) that calls multiple methods like mapTagAInfo(details, xmlRootElement), mapTagBInfo(details, xmlRootElement) etc. on details(i.e. instance of Details.java) something like following -

public class Mapper {
 ....

public Details mapInfo(XmlElement xmlRootElement) {
  Details details = new Details();
  mapTagAInfo(details, xmlRootElement)
  mapTagBInfo(details, xmlRootElement)
  mapTagCInfo(details, xmlRootElement)
 ....
 return details;
}

private void mapTagAInfo(details, xmlRootElement) {
  stp1: Extract <TagA> tag element info using a utility which reads the xml document
  stp2: use the stp1 info and convert to internal model POJO TagAInfo and 
  add to details (details.addTagAInfo(tagAInfo))
}

Question: The current implementation makes the code look very ugly(as in a single class Mapper.java multiple things are happening), so wanted to know if I can use some design pattern to improve the code ? If so, please suggest what design pattern to use and an example explaining the design pattern usage would help a lot.