[EDIT] 収支Entityの主キーの型を修正しました。

src/main/java/com/example/demo/app/domain/model/TransactionModel.java

@@ -0,0 +1,22 @@
+package com.example.demo.app.domain.model;
+
+import java.time.LocalDate;
+
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+
+@Getter
+@AllArgsConstructor
+public class TransactionModel {
+
+	private Long transactionId;
+	
+	private Long userId;
+	
+	private Long categoryId;
+	
+	private Integer amount;
+	
+	private LocalDate transactionDate;
+	
+}

src/main/java/com/example/demo/app/infra/entity/TransactionEntity.java

@@ -26,7 +26,7 @@ public class TransactionEntity {
 	@Id
 	@GeneratedValue(strategy = GenerationType.IDENTITY)
 	@Column(name = "transaction_id")
-	private Integer transactionId;
+	private Long transactionId;
 	
 	@Column(name = "amount", nullable = false)
 	private Integer amount;

src/main/java/com/example/demo/app/presentation/form/TransactionForm.java

@@ -1,5 +1,10 @@
 package com.example.demo.app.presentation.form;
 
+import java.time.LocalDate;
+import java.util.List;
+
+import com.example.demo.app.domain.model.TransactionModel;
+
 import lombok.AllArgsConstructor;
 import lombok.Data;
 import lombok.NoArgsConstructor;
@@ -9,6 +14,27 @@ import lombok.NoArgsConstructor;
 @NoArgsConstructor
 public class TransactionForm {
 
+	private Long transactionId;
 
+	private Long userId;
+
+	private Long categoryId;
+
+	private Integer amount;
+
+	private LocalDate transactionDate;
+
+	public static TransactionForm convertFrom(TransactionModel transactionModel) {
+		return new TransactionForm(
+				transactionModel.getTransactionId(),
+				transactionModel.getUserId(),
+				transactionModel.getCategoryId(),
+				transactionModel.getAmount(),
+				transactionModel.getTransactionDate());
+	}
+
+	public static List<TransactionForm> convertFrom(List<TransactionModel> transactionModelList) {
+		return transactionModelList.stream().map(TransactionForm::convertFrom).toList();
+	}
 
 }