For the flow, set [Loop by Number of Data] process after [Get sheet names] process of an Excel adapter.
　-- 
　[Get Sheet Names]-> [Loop by Number of Data]-> [Mapper]
　-- 

• [Loop by Number of Data]

URL:https://www.hulft.com/help/en-us/DataSpider/dss42sp2/help/en/adapter/basic/foreach.html

　In addition, since the output schema of the sheet name list acquisition process is XML type, it is necessary to set [Sepatation path] in repetition (number of data) processing.
　The sheet name list acquisition process is the following XML type schema.

　------------ 
　<book> 
　 <Sheet> {sheet name 1} </ sheet>
　 <Sheet> {sheet name 2} </ sheet>
　 ... 
　</book> 
　------------ 

　Therefore, by setting [/ book / sheet] in [Separation path] of [XML data processing] tab in the property of repetition (number of data) processing, it is possible to carry out reading processing for the number of sheets.
　In addition, the output schema of the sheet name list acquisition process is not set automatically, so it needs to be set individually.
　Please refer to the following help for the schema of sheet name list acquisition process.

• [Sheet Name Lists]-[Schema]

URL:https://www.hulft.com/help/en-us/DataSpider/dss42sp2/help/en/adapter/file/excel_get_sheet_name.html