2 API calls, one passes values to second

You started me on the correct path, so I thank you. Here was the final solution. 

After I implemented your recommended changes, I was getting a firewall error saying that my query couldnt call the MergedList because it contained another call. So instead of calling two API calls in two Tables, I combined them into one. 

let
Source = Json.Document(Web.Contents("https://APIURLservice-now.com/api/now/table/APITABLEequipment_reserve_transfer_order?sysparm_query=u_completedBETWEENlastWeek()now()&sysparm_fields=sys_id,u_completed")),
#"Converted to Table" = Record.ToTable(Source),
#"Expanded Value" = Table.ExpandListColumn(#"Converted to Table", "Value"),
#"Expanded Value1" = Table.ExpandRecordColumn(#"Expanded Value", "Value", {"sys_id"}, {"Value.sys_id"}),
#"Removed Columns" = Table.RemoveColumns(#"Expanded Value1",{"Name"}),
#"Changed Type" = Table.TransformColumnTypes(#"Removed Columns",{{"Value.sys_id", type text}}),
#"Transposed Table" = Table.Transpose(#"Changed Type"),
Custom1 = Table.ColumnNames(#"Transposed Table"),
#"Converted to Table1" = Table.FromList(Custom1, Splitter.SplitByNothing(), null, null, ExtraValues.Error),
Custom2 = Table.AddColumn(#"Converted to Table1","Custom", each Text.End([Column1],1)),
#"Changed Type1" = Table.TransformColumnTypes(Custom2,{{"Custom", type date}}),
#"Removed Errors" = Table.RemoveRowsWithErrors(#"Changed Type1", {"Custom"}),
Column1 = #"Removed Errors"[Column1],
Custom3 = Table.RemoveColumns(#"Transposed Table",Column1),
Custom4 = Table.ColumnNames(Custom3),
Custom5 = Table.CombineColumns(Custom3, Custom4, Combiner.CombineTextByDelimiter(","),"Merged"),
#"Changed Type2" = Table.TransformColumnTypes(Custom5,{{"Merged", type text}}),
TransferNumber = Table.ToList(Table.SelectColumns( #"Changed Type2",{"Merged"})){0},
Final = Json.Document(Web.Contents("https://APIURLservice-now.com/api/now/table/APITABLEquipment_reserve_transfer_order_line_item?sysparm_query=parts_transfer_orderIN" & TransferNumber & "&sysparm_display_value=all")),
#"Converted to Table2" = Record.ToTable(Final),
#"Expanded Value2" = Table.ExpandListColumn(#"Converted to Table2", "Value"),
#"Expanded Value3" = Table.ExpandRecordColumn(#"Expanded Value2", "Value", {"parts_transfer_order", "short_description", "u_asset", "u_asset_condition", "requested_quantity", "sys_mod_count", "description", "received", "sys_updated_on", "sys_domain_path", "received_quantity", "remaining_quantity", "sys_class_name", "number", "sys_id", "u_reason", "sys_updated_by", "shipment_tracking_link", "sys_created_on", "parts", "shipment_tracking_number", "sys_created_by", "status"}, {"Value.parts_transfer_order", "Value.short_description", "Value.u_asset", "Value.u_asset_condition", "Value.requested_quantity", "Value.sys_mod_count", "Value.description", "Value.received", "Value.sys_updated_on", "Value.sys_domain_path", "Value.received_quantity", "Value.remaining_quantity", "Value.sys_class_name", "Value.number", "Value.sys_id", "Value.u_reason", "Value.sys_updated_by", "Value.shipment_tracking_link", "Value.sys_created_on", "Value.parts", "Value.shipment_tracking_number", "Value.sys_created_by", "Value.status"}),
#"Expanded Value.parts_transfer_order" = Table.ExpandRecordColumn(#"Expanded Value3", "Value.parts_transfer_order", {"display_value", "value"}, {"Value.parts_transfer_order.display_value", "Value.parts_transfer_order.value"})
in
#"Expanded Value.parts_transfer_order"