createProductWithManyImage.js

const { getUserId } = require("../../utils");
const { processUpload } = require("../../modules/fileApi");

const supplierProduct = {
  async createSupplierProduct(parent, args, ctx, info) {
    const images = await Promise.all(
      args.files.map(file => processUpload(file, ctx))
    );

    const imageId = await images.map(image => image.id);

    return ctx.db.mutation.createSupplierProduct(
      {
        data: {
          name: args.name,
          description: args.description,
          detail: args.detail,
          tags: [...args.tags],
          inventory: args.inventory,
          retailPrice: args.retailPrice,
          wholesalePrice: args.wholesalePrice,
          category: {
            connect: { id: args.categoryId }
          },
          images: {
            connect: { id: [...imageId] }
          }
        }
      },
      info
    );
  }
};

module.exports = { supplierProduct };

connect accepts an array of objects. Doing something like below should help:

return ctx.db.mutation.createSupplierProduct(
      {
        data: {
          name: args.name,
          description: args.description,
          detail: args.detail,
          tags: [...args.tags],
          inventory: args.inventory,
          retailPrice: args.retailPrice,
          wholesalePrice: args.wholesalePrice,
          category: {
            connect: { id: args.categoryId }
          },
          images: {
            connect:[ { id: <image_id_1> }, {id: <image_id_2>}, ...]
          }
        }
      },
      info
    );