warning  in ./src/main.js

export 'default' (imported as 'Vue') was not found in 'vue' (possible exports: BaseTransition, BaseTransitionPropsValidators, Comment, DeprecationTypes, EffectScope, ErrorCodes, ErrorTypeStrings, F
ragment, KeepAlive, ReactiveEffect, Static, Suspense, Teleport, Text, TrackOpTypes, Transition, TransitionGroup, TriggerOpTypes, VueElement, assertNumber, callWithAsyncErrorHandling, callWithErrorH
andling, camelize, capitalize, cloneVNode, compatUtils, compile, computed, createApp, createBlock, createCommentVNode, createElementBlock, createElementVNode, createHydrationRenderer, createPropsRe
stProxy, createRenderer, createSSRApp, createSlots, createStaticVNode, createTextVNode, createVNode, customRef, defineAsyncComponent, defineComponent, defineCustomElement, defineEmits, defineExpose
, defineModel, defineOptions, defineProps, defineSSRCustomElement, defineSlots, devtools, effect, effectScope, getCurrentInstance, getCurrentScope, getCurrentWatcher, getTransitionRawChildren, guar
dReactiveProps, h, handleError, hasInjectionContext, hydrate, hydrateOnIdle, hydrateOnInteraction, hydrateOnMediaQuery, hydrateOnVisible, initCustomFormatter, initDirectivesForSSR, inject, isMemoSa
me, isProxy, isReactive, isReadonly, isRef, isRuntimeOnly, isShallow, isVNode, markRaw, mergeDefaults, mergeModels, mergeProps, nextTick, normalizeClass, normalizeProps, normalizeStyle, onActivated
, onBeforeMount, onBeforeUnmount, onBeforeUpdate, onDeactivated, onErrorCaptured, onMounted, onRenderTracked, onRenderTriggered, onScopeDispose, onServerPrefetch, onUnmounted, onUpdated, onWatcherC
leanup, openBlock, popScopeId, provide, proxyRefs, pushScopeId, queuePostFlushCb, reactive, readonly, ref, registerRuntimeCompiler, render, renderList, renderSlot, resolveComponent, resolveDirectiv
e, resolveDynamicComponent, resolveFilter, resolveTransitionHooks, setBlockTracking, setDevtoolsHook, setTransitionHooks, shallowReactive, shallowReadonly, shallowRef, ssrContextKey, ssrUtils, stop
, toDisplayString, toHandlerKey, toHandlers, toRaw, toRef, toRefs, toValue, transformVNodeArgs, triggerRef, unref, useAttrs, useCssModule, useCssVars, useHost, useId, useModel, useSSRContext, useSh
adowRoot, useSlots, useTemplateRef, useTransitionState, vModelCheckbox, vModelDynamic, vModelRadio, vModelSelect, vModelText, vShow, version, warn, watch, watchEffect, watchPostEffect, watchSyncEff
ect, withAsyncContext, withCtx, withDefaults, withDirectives, withKeys, withMemo, withModifiers, withScopeId)

原因是你在vue3的项目中使用了vue2的语法。